* 1 2640 1250 2840 4250 440 1820 " This is simply the current temperature measured" " by a properly sheltered thermometer." * 2 2000 2300 2900 4300 1500 1900 " This is the amount of water vapor present in" " the air as a percentage of the 'saturation' value," " that is, the most vapor pressure possible at that" " temperature. Since saturation vapor pressure" " increases with temperature, the relative humidity" " varies inversely with the temperature, assuming" " the actual amount of water vapor is constant." * 3 2000 3000 2900 5000 2200 2200 " Dew point is the temperature at which the air, with the" " current amount of water vapor, would reach 'saturation'," " forming dew, frost, fog, or precipitation. When the" " relative humidity reaches 100%, the dew point equals" " the temperature; otherwise the dew point is less than" " the temperature. Dew point is an especially useful" " measure of humidity because it depends directly on the" " actual amount of water vapor present - unlike relative" " humidity, which can vary dramatically with temperature" " changes, even though the air's moisture content may be" " fixed. Typically, dew point changes only slightly" " during a given day." * 4 2000 3750 2900 5100 2950 2250 " Wet bulb temperature is the temperature reported by a" " thermometer whose bulb is covered by a wet wick. By" " comparing this temperature to the actual ('dry bulb')" " temperature, the dew point and the relative humidity" " can be calculated. An instrument consisting of such" " wet and dry bulbs (often ventilated by a fan or by" " swinging through the air) is called a psychrometer and" " is still one of the more accurate means of determining" " humidity. The lower the relative humidity, the greater" " the 'wet bulb depression', since drier air allows more" " evaporation, which in turn cools the wet bulb. When the" " wet bulb is equal to the dry bulb, no net evaporation is" " taking place because the air is saturated, with 100%" " relative humidity and a dew point equal to both the wet" " and dry bulb temperatures." * 5 2000 3200 2900 5640 2380 2540 " Barometric pressure is simply the pressure applied by the" " surrounding air. It decreases with altitude (since higher" " up there is less air on top to apply such pressure) and is" " often relatively low during inclement weather. It is commonly" " measured in either of two units - millibars (also called" " hectopascals) and inches of mercury (in reference to the" " height of a column of mercury supported by this pressure in" " a mercury barometer. Average sea level pressure is about 29.9" " inches of mercury (in.Hg) or about 1013 millibars (mb). You" " may choose to enter either the station pressure or the commonly" " reported sea level value. Values outside the range of 15-33" " in.Hg or 500-1100 mb will not be accepted." * 6 200 5160 270 9100 4340 4300 " Wind speed should ideally be measured about 10 meters (33 feet) above the ground in an area relatively" " free of trees, buildings, and other obstructions. Note the four options for units; wind speed will" " be output using the same units you use for input. Speeds over 200 mi/hr will not be accepted. The" " following table, adapted from the well-known Beaufort scale, may help if you must estimate wind speed." " " " MILES/HR KM/HR KNOTS METERS/SEC DESCRIPTION" " " " 1-3 1-5 1-3 0.5-1.5 Rising smoke drifts, wind barely felt on face" " 4-7 6-11 4-6 2-3 Light breeze, leaves rustle" " 8-12 12-19 7-10 4-5 Gentle breeze, leaves and twigs in constant motion" " 13-18 20-29 11-16 6-8 Paper blown about, flag extended, small branches sway" " 19-24 30-39 17-21 9-11 Small trees sway, flag fully extended and rippling" " 25-31 40-50 22-28 12-14 Trees sway, flag ripples loudly, some whistling heard" " in wires, some difficulty walking " " 32-38 51-61 28-34 15-17 Large trees sway, difficult to walk" " 39-46 62-73 35-41 18-20 Twigs and weaker branches break off trees" " " " For wind direction, an average direction from which the wind has been blowing for the last few minutes" " is appropriate. Enter this direction using the scroll bar; clicking in the bar jumps 22.5 degrees while" " clicking on the arrows moves 5 degrees at a time. You may use numeric directions (azimuth 0 to 360) or" " abbreviated text ('letters') such as 'NNE', 'NE', 'ENE', etc. By default, level 1 (about 60 mb above" " surface) will be set to the same value as your entered surface wind direction, though you can change" " level 1 wind direction separately if necessary." * 7 2900 3800 260 9140 3000 4300 " WXSIM models the atmosphere as a near-surface ('boundary') layer plus 5 higher levels. The two highest" " levels, 4 and 5, are centered about the 500 millibar and 300 millibar pressure levels, respectively." " The three lower ones' exact heights and pressure levels depend on surface elevation and barometric" " pressure, but are designed to match the 925, 850, and 700 millibar levels when the station (NOT sea" " level) pressure is 985 mb - typical of elevations around 280 meters (920 feet) under average conditions." " " " Cloud levels refer here to the atmospheric level in which the BASE of the cloud is located. The exact" " heights and pressures of the atmospheric levels will be given after the calibration run, but the table" " below should provide a rough guide to the cloud heights for data entry purposes." " " " Level 1 about 530 meters = 1740 feet above SURFACE" " Level 2 about 1230 meters = 4035 feet above SURFACE" " Level 3 about 2820 meters = 9250 feet above SURFACE" " Level 4 about 5700 meters = 18700 feet above SEA LEVEL" " Level 5 about 9300 meters = 30500 feet above SEA LEVEL" * 8 2800 2700 1700 6150 1860 2800 " 'Coverage' refers simply to the percentage of the sky covered by" " clouds. Enter this for each level using the scroll bar. Clicking" " in the bar changes coverage by 10% while clicking the end arrows" " changes it by 1% at a time. It may be difficult to determine cloud" " cover at higher levels when lower clouds are present, but ideally" " the high level coverages should be entered as they would appear if" " no lower clouds were present. Notice that changing coverage auto-" " matically changes the opacity (cloud 'thickness' or 'density'), but" " if needed, you can adjust the opacity separately after coverage is set." * 9 2750 3960 1600 6550 3140 3000 " 'Opacity' (or 'opaqueness') refers to how dense or thick a cloud appears." " Here, this is essentially a subjective judgement, reported on a scale of" " 0 to 5, but should be aided by the following guidelines." " " " 1. Very thin - bright sun in day; stars easily visible at night." " 2. Thin - sun, moon fairly bright; only brightest stars visible." " 3. Medium - sun, perhaps moon, dimly visible; no stars visible." " 4. Fairly dense - sun not visible, but usually no precipitation." " 5. Very dense - dark gray sky, usually with precipitation." " " " Thin cirrus usually rate a 1, though cirrostratus might reach 2. A value" " of 3 might be typical of altostratus or relatively thin cumulus or stratus" " clouds. Most stratus and sigificantly developed cumulus clouds rate a 4." " Only low clouds likely to produce precipitation are likely to exceed 4.5." " Note that changing coverage will automatically change the opacity, which" " may, if needed, be readjusted afterwards without affecting the coverage." * 10 2800 2000 1420 6780 1180 3080 " This is the direction from which the wind is blowing at the level in question." " This can be determined either by watching any clouds that happen to be at" " that level or from a sounding or other upper air information. This information" " is used only for aiding in the default upper air temperature routine and so is" " not crucial if you will be supplying upper air temperatures anyway. Note that" " upper air wind speeds are not considered in this program." * 11 4400 1240 1800 4300 400 1800 " This is a text description of the combined cloud" " cover you have entered in levels 1 and 2." * 12 4400 1240 3300 4300 400 1800 " This is a text description of the combined cloud" " cover you have entered in levels 3 and 4." * 13 4400 1240 5300 3400 400 1500 " This is a text description of the cloud" " cover you have entered in level 5." * 14 240 4280 1280 6920 3500 3000 " This option activates a routine which attempts to model the development and" " dissipation of convective clouds, which may range from widely scattered" " 'fair weather cumulus' to thunderstorms. These clouds are assumed to have" " bases in level 2, generally 900 to 2000 meters (about 3000 to 6500 feet) above" " the surface. This is appropriate except in desert climates, where they are" " usually higher." " " " The algorithm for this routine includes factors such as surface temperature" " and dew point, dew points in levels 1 and 2, barometric pressure, atmospheric" " stability, and cloud cover input by the user. If cloud development is suffi-" " cient, the program will suggest a chance of showers, but it is up to the user" " to initiate any precipitation. Also note that in cool or dry weather these" " clouds are unlikely to form (or dissipate if you entered level 2 clouds)." " " " If you use interrupts for precipitation or low clouds during the forecast run," " the routine will be disabled. An exception is if you use interrupts '{' or '}'," " which decrease or increase, respectively, level 2 cloud cover without turning" " off the routine. You can also activate it at any time during the run by using" " interrupt '?'." * 15 480 4000 1000 7640 3200 3360 " Activating this routine allows the program to attempt to model the development and" " dissipation of low stratus clouds that may form overnight in humid conditions. These" " clouds are assumed to occupy level 1, about 180 to 900 meters (600 to 3000 feet)" " above the surface. These clouds vary with the diurnal heating/cooling cycle because" " level 1 is close enough to the surface to 'feel' surface heating and cooling effects." " " " These clouds are most likely to occur when the sky above the clouds is clear and there" " is abundant moisture in level 1. The level 1 dew point is either calculated using a" " default, surface-based routine or entered by the user. Usually these clouds will 'burn" " off' with daytime heating, but during cooler times of year or near a large body of" " water with an on-shore breeze, they may fail to do so and the site may become 'socked in'" " with a low overcast. If development of these clouds is sufficient, the program may" " suggest a chance of drizzle, but only the user can initiate this." " " " If you use interrupts for precipitation or low clouds during the forecast run, the routine" " will be disabled. You can activate it at any time during the run by using interrupt'/'." * 16 1500 3000 1100 7540 2180 3420 " The auto haze routine estimates a likely amount of haze for a semi-urban site under" " the input (and then modeled) weather conditions. Generally, higher humidity, lighter" " winds, and a more stable atmosphere are assumed to contribute to more particulate in" " the lower atmosphere, restricting horizontal visibility and reducing both incoming" " solar and outgoing longwave radiation somewhat. Many other variables, such as local" " sources of pollution, are important here, so that the routine can easily be rendered" " inaccurate, but it still supplies a reasonable 'educated guess' under most conditions." " " " The routine will be disabled if you use interrupts 'j' or 'k' (decrease and increase" " haze, respectively) or ';'. This last one actually toggles auto haze between the on" " and off states, so it may also be used to activate the routine." * 17 1400 3800 1120 7440 3000 3420 " Dew and frost require energy to evaporate - energy that would otherwise be used to" " warm the surface and the air above it. For this reason, the morning temperature rise" " will be slowed somewhat if such moisture is present in the morning. Also, the resul-" " ting water vapor will add somewhat to the afternoon's humidity." " " " If the calibration run includes the formation of dew, frost, or fog, these will be" " assumed to represent the initial conditions by default. If you wish to specify dew" " or frost yourself, you may enter it here using a subjective scale ranging from 0 (none)" " to 5 (extremely heavy). Generally, a value of 1 might indicate condensation only on" " car tops, 2 would indicate a lot on cars plus rather damp grass, 3 would indicate very" " wet grass, and 4 would look like it had rained overnight. 5 would rarely be used." " " " A quantitative indication of the amount of dew, fog, etc. is provided by the 'potential" " dew point', which is the dew point likely later in the day after all the dew, etc. has" " evaporated (though if the level 1 dew point is low, mixing may hold surface dew point" " somewhat below this potential value)." * 18 3500 1800 1120 7400 990 3400 " This is a quantitative indication of the amount of dew, fog, etc. - either entered by" " the user or assumed on the basis of the calibration run. It represents the dew point" " likely later in the day after all this surface moisture has evaporated. Note that other" " factors, such as advection, precipitation, and mixing with air above may make the" " actual (and modeled) dew point later in the day somewhat different." * 19 960 3500 1100 7500 2700 3440 " If you do not opt for auto haze, you can enter the haze amount here; it will then" " remain constant during the forecast run unless you increase or decrease it by 0.5" " using interrupts 'k' or 'j', respectively, or activate auto haze using ';'. This" " haze thickness uses a subjective scale, described as:" " " " 0. Very good visibility, deep blue skies in daytime." " 1. Fair visibility, skies blue but somewhat pale, becoming whitish near horizon." " 2. Rather poor visibility, whitish blue sky with cloud edges indistinct." " 3. Very poor visibilty, whitish gray or brown sky, smoggy with sunlight reddened." " " " Note that a visibility estimate is shown below, though this includes effects of any" " fog or precipitation as well. Haze is assumed in this program to both reduce incoming" " sunlight and absorb and re-emit longwave radiation from the ground, thereby reducing" " diurnal temperature ranges somewhat." * 20 330 4960 1060 7460 4140 3380 " If fog is present, you may enter it here. The program may well produce fog anyway," " but your estimate of its present density will be quite useful. You are asked to enter" " a subjective value (using the scroll bar) on a scale of 0 to 3 as follows (please note" " that the qualitative descriptions here may differ from some official uses):" " " " 0. None." " 1. Fairly light - horizontal visibility typically about 5 miles (8 kilometers)." " 2. Moderate to dense - visibility about 1 mile (1-2 kilometers)." " 3. Very dense - visibility under 1/8 mile (200 meters)." " " " A visibility estimate will be shown below, but note that it includes the effects of haze" " and precipitation as well. If, later in the program run, fog fails to 'lift' when you" " think from experience that it should, you can eliminate it with interrupt '^', which" " actually toggles the fog routine between on and off states (by default it is 'on')." " " " If, after using the program for a while, you find fog predictions under- or over-done," " you can make adjustments to the 'fog sensitivity', under the 'Customize' menu item." " " " Fog that you enter (or produced during the calibration run if you don't enter a value)" " potentially add to the days dew point - assuming it later evaporates. This, along with" " default or entered dew or frost, contribute to the 'potential dew point', as indicated." * 21 2400 2460 1200 7220 1620 3400 " This visibility estimate is based upon default or entered values for haze, fog, and" " precipitation. The combined effect is assumed to be additive, where the visibilty" " is an exponential function of the negative of the sum of these three contributions." " Of course visibilty depends on what one is looking at, but the values here are" " intended to correspond roughly to values reported officially for aviation purposes." " Here it serves simply as a way to enter appropriate fog, haze, and precip amounts." " Note that in the output, visibility's units will be in (statute) miles if you are using" " Fahrenheit, and in kilometers if you are using Celsius." * 22 600 5560 100 7020 4750 3100 " Heavily developed urban areas (and in some cases large, busy airports) often" " have warmer temperatures than surrounding, more rural, areas. This is most" " significant on clear, calm nights, when such differences may exceed 10 degrees" " F (6 Celsius degrees); daytime differences are usually much smaller. Though" " this program has been calibrated using mainly 'suburban' (a sort of average of" " rural and urban) data, this 'heat island' adjustment allows you to describe your" " site more appropriately. You may notice that stronger heat island effects tend" " to yield temperatures closer to the 'hill' than the 'valley' temperatures (see" " output menu option #2), with 'rural' closer to 'valley'. The default value is" " usually 50, but other values may have been assumed for some on-file sites, so" " take note and adjust if needed. You may notice some very slight differences in" " the surface temperatures used in the upper air and advection routines and your" " input initial temperature if the heat island effect is not 50, but this is con-" " sidered appropriate by the program." " " " As for making the subjective judgement called for here, some experience and" " experimentation may be called for, but the following should give a rough idea of" " appropriate values." " " " 0. Very rural, undeveloped land, especially relative low elevation spots." " 25. Typical 'countryside' or outermost suburban areas." " 50. Typical city of 50,000 or so, or average suburb of large city." " 75. Densely populated/developed area, such as downtown city of 500,000." " 100. Downtown of very large city, especially relative high elevation spots." * 23 2900 1620 2700 6700 800 3120 " Click 'Yes' only if precipitation is currently falling. It is not otherwise" " necessary to click 'No' unless 'Current Precip' is highlighted in red as the" " result of an earlier 'Yes'. In otherwords, blue means 'off' and red means 'on'." " If you click 'Yes', you will be asked for more information on a separate form." * 24 2900 2000 2560 6860 1180 3200 " Click 'Yes' if recent precipitation has been either unusually light or heavy;" " otherwise the program assumes a soil moisture representative of the site's" " annual average. It is not otherwise necessary to click 'No' unless you need" " to undo the result of an earlier 'Yes' click, which will have highlighted 'Recent" " Precip' in red. In otherwords, blue means'off' and red means 'on'. If you" " click 'Yes', you will be asked for more information on a separate form." * 25 2900 1780 2660 6740 980 3160 " Click 'Yes' if there is currently snow or ice on the ground. it is not otherwise" " necessary to click 'No' except to undo the result of an earlier 'Yes' click, in" " which * 'Snow/Ice Cover' will be highlighted in red. In other words, red" " means there is snow/ice on the ground and blue means there is not. If you" " click 'Yes', you will be asked for further information on a separate form." * 26 2900 2000 2560 6860 1180 3200 " Click 'Yes' if recent temperatures have been either unusually high or low;" " otherwise the program assumes a soil temperature representative of the site's" " seasonal average. It is not otherwise necessary to click 'No' unless you need" " to undo the result of an earlier 'Yes' click, which will have highlighted 'Recent" " Temps' in red. In otherwords, blue means 'use defaults' and red means 'use" " user-input data'. If you click 'Yes', you will be asked for more information"" on a separate form." * 27 850 5140 2480 6960 4330 3250 " The program can model two special types of diurnal wind cycles: the sea" " breeze cycle, in which low level winds to flow from the cooler surface towards" " the warmer one, and the mountain/valley cycle, in which cool air tends to" " flow downhill at night and warm air uphill in the daytime. Both cycles are" " most pronounced in fair weather with otherwise light winds, as such conditions" " allow greater local differences and changes in temperature." " " " If you click 'Yes' here, the program will sort out a 'base' wind velocity vector" " from the current wind data and the expected breeze effect and use these to" " predict the changing wind speed and direction. Clicking 'Yes' will also show" " you a form asking for confirmation or new values for relevant variables." " " " If you have planned (manually or by importing READY or GFS data) changes in" " wind speed or direction, these are assumed by the program to apply to the base" " wind velocity, so the output wind may be somewhat different from planned." " Likewise, any wind changes directed by NGM or NAM FOUS data are applied to" " the base wind." " " " It is not otherwise necessary to click no except to undo the result of an earlier" " 'Yes' click, in which case 'Diurnal Breeze' will be highlighted in red. In other" " words, red means the routine is 'on' and blue means it is 'off'. You can also" " activate this routine during the forecast run with interrupt '~'." * 28 1600 3360 2480 6950 2550 3250 " Temperature data (max and min for the last 24 hours) and elevation data for a" " site several hundred miles or km to the west may help forecast accuracy under" " the assumption that large scale weather patterns migrate from west to east in" " the mid latitudes, which is often, but not always the case. Basically, this" " option, activated by clicking 'Yes', is a 'catch-all' way of including effects such" " as changing upper air temperatures, weak advection, etc. and is somewhat" " redundant with (and probably inferior to, but easier than) the other advection" " options. If both this routine and other advection are in use simultaneously," " present routine will 'take a back seat' to the other advection, acting with a" " much reduced 'potency'." " " " It is not necessary to click 'No' here if you do not wish to use the routine," " unless 'Site to West' is highlighted in red as the result of an earlier 'Yes' click." * 29 1640 3980 3120 4650 3160 2040 " Enter the starting date for the forecast with the" " month, day, and year, separated by slashes, dashes," " or dots. Default is current date on computer's" " clock. NOTE: This date should correspond to your" " LOCAL time, NOT GMT. You may enter or import" " GMT times, but the date should be your local date." " For example, if you are on Eastern Time (5 hours" " behind GMT), 10PM on 1/12/01 could be entered" " as either 10PM (or 22:00) on 1/12/01 or 3z" " (or 3:00z) on 1/12/01, but NOT 3Z on 1/13/01." " The reason for this is that certain routines rely" " on having 'midnight' actually occur at night!" " " " NOTE: In many countries Da/Mo/Yr is the standard" " format. This convention is supported as well, and" " can be selected under the 'Customize' menu item." * 30 1640 2600 1840 4800 1780 2120 " Enter the starting time for the forecast. This may" " be in whole hours (i.e. '15') or hours and minutes" " (using colon as separator) and may be in 24 hour time" " or 12 hour, followed by 'a' or 'p' to denote AM or PM." " You may also enter 'Greenwich Mean Time' (or 'Zulu')" " by following the time immediately with 'z' (i.e. '12z')." " Default is current time on computer's clock. Please" " read more on this by clicking on the blue 'Mo/Da/Yr'" " or 'Da/Mo/Yr' caption just to the left." * 31 1640 1050 1840 4460 240 1940 " Enter a check if daylight savings time is in effect." * 32 1640 1420 1840 4600 600 2000 " Time when top edge of sun first appears on horizon." " (Includes effect of atmospheric refraction and is" " usually accurate to within about two minutes)." * 33 1640 1420 1840 4920 600 2180 " Time when top edge of sun disappears below horizon." " (Includes effect of atmospheric refraction and is usually" " accurate to within about two minutes)." * 34 1640 1420 1840 4920 600 2180 " Altitude of sun above horizon at initialization time." " (In degrees. Does NOT include effect of atmospheric" " refraction but is usually accurate to within one degree)." * 35 1640 1820 1840 4920 1000 2180 " This is the time in the morning when the temperature is" " expected to have risen halfway from the morning low to" " the afternoon high. Used as starting time for calibration" " run if actual forecast time is afterwards but before the" " evening midpoint temperature ('Midpt 2')." * 36 1640 1820 1840 4940 1000 2180 " This is the time in the evening when the temperature is" " expected to have fallen halfway from the afternoon high" " to the morning low. Used as starting time for calibration" " run if actual forecast time is afterwards but before the" " morning midpoint temperature ('Midpt 1')." * 37 1640 1420 1840 4800 600 2180 " This is the sun's maximum altitude (in degrees) above" " the horizon for the day. It occurs around LOCAL noon," " midway between sunrise and sunset." * 38 4250 1420 2500 4780 600 2180 " Click on the current predominant type of precipitation." " This information helps the program determine an initial" " upper air temperature profile." * 39 4000 2070 2640 4760 1250 2180 " This refers to the ratio of the snow (or ice) depth to" " that of the water resulting from melting it down. For" " wet snow this ratio is around 6, while dry, fluffy snow" " may exceed 15. Solid ice rates just over 1, while ice" " pellets yield close to 3. The best way to check is" " simply to melt a core sample." * 40 4100 2140 2200 4880 1340 2180 " If the weather pattern has been fairly stagnant, with" " no significant frontal passages or temperature changes" " in the last day or two, the maximum and minimum temp-" " eratures for the last 24 hours can help the program" " establish an accurate initial characteristic temperature" " for the air mass. Otherwise, this option should not" " be checked." * 41 4100 2140 2160 4980 1340 2180 " Mean temperature (averages of daily highs and lows) for" " the last four days is correlated with near-surface soil" " temperatures and therefore can influence the overlying" " air temperature. This information is useful whether the" " air mass has changed recently or not. You may find this" " to be a rather minor influence, but it should generally" " refine the forecast." * 42 1800 4590 3160 5090 3770 2280 " This option allows you to import surface data (METAR or" " SYNOPtic) to automatically fill out the initial data entry" " form. It is assumed that you have downloaded a file of" " raw METAR or SYNOP data containing your site ID. The" " last entry found that matches your site will be used." " Note that the reported visibilty is used in estimating haze," " fog, and/or precip intensities; you should inspect this" " and all the data before making your forecast run. The" " 'Exclude SPECI' (for METAR only) option allows you to" " omit between-hours special reports (to help synchronize" " with advection data). Note: Some individual SYNOP" " reports may lack a time field, in which case you will need" " to supply the observation time yourself." " " " GFS data, interpolated in time and location, and adjusted" " for elevation, can also be used to initialize much of the" " form, but this is mostly appropriate for sites far from" " METAR or synoptic reporting stations. MOS is available" " only for advection purposes after wind shifts." * 43 1800 5600 3160 5220 4780 2380 " This option allows you to import surface data (METAR or" " SYNOPtic) to automatically supply upwind site data for the" " regional data advection routine. It is assumed that you" " have downloaded a file of raw data containing the site ID's" " of at least some of the upwind sites known to WXSIM." " The last entry found that matches each site will be used." " You will have an opportunity to select which of these" " sites (including those for which no data is found) to use" " in the routine, along with the chance to modify data if" " needed. More information can be found by clicking on" " the blue caption to the 'Regional Data' check box on the" " advection form that appears before the forecast run. The" " 'Exclude SPECI' (for METAR only) option lets you omit" " special between-hours reports to help keep advection data" " more synchronous." "" " You can also use GFS model data, interpolated in time and" " location from a 20 x 20 degree grid, with adjustments for" " elevation. This is not recommended for initial advection" " data, but may be very useful after wind shifts. The MOS" " (Model Output Statistics, from the GFS and NAM models) is" " available for North American users, but is intended only" " for advection after wind shifts, and it runs out within" " about 60 hours, after which GFS advection may be used" " out to about 7 days." * 44 1100 5960 3800 5560 5120 2480 " This and the other FOUS option allow you to import FOUS" " (FOrecast U.S.) block data from the NAM or NGM model. It" " is assumed that you have downloaded a file of raw FOUS" " data containing data for at least one of the three sites known" " by WXSIM to be closest to yours. The last entry found" " that matches each site will be used. If some data is found" " to be 12 hours older that other data (including any other" " FOUS data found), it will still be included, with the start" " time difference automatically taken into account. If 2 or 3" " sites are found, a properly weighted average of the data will" " be used to interpolate for your home site, including use of" " elevation data for all sites used." " " " All the data types supplied are displayed graphically for the" " full 48 hours, mixed with any other FOUS data to a degree" " determined by the user with the NAM-NGM scroll bar. Also," " some of the data can be weighted into the WXSIM model run" " itself, by clicking 'Activate FOUS' and selecting the desired" " 'weights'. Since these weights involve exponential approach" " to the NAM/NGM values, they are given in terms of the time in" " hours to get halfway to the FOUS values. Shorter 'half-life'" " means that WXSIM values will 'hug' the FOUS ones more" " closely." " " " NOTE: The NGM model was discontinued in 2009. The option" " remains here solely for legacy purposes, such as re-running" " old forecasts." * 45 300 6460 3800 5270 5640 2400 " This option allows you to import raw TTAA radiosonde" " observations. It is assumed that you have downloaded" " a file of such data containing the synoptic codes of" " at least one of the three RAOB sites provided for in" " your custom site file. The last entry that matches" " each site will be used. If data for two or more of the" " sites is found, the program will produce a weighted" " average to best represent your site. Differences in" " elevation are considered as well. Only the 'mandatory'" " levels of 1000, 925, 850, 700, 500, 400, and 300 mb," " plus the surface are used, and the data types used are" " height (meters), temperature, and dew point (Celsius)." "" " This information does not directly affect WXSIM's output," " but you can use it to help initialize the upper air data," " as the temperature and dew point soundings versus height" " will be displayed with the program's default 'educated" " guesses', and also FOUS forecast soundings, if you also" " downloaded NGM or NAM FOUS data. Note though, that" " upper air conditions do change during the day, especially" " at the lower levels, so old RAOB data may not represent" " current conditions very well." "" " There is, however, a source for TTAA format analysis data" " for the RUC-2 and MAPS models. This data is derived" " partly from aircraft reports and is available hourly. For" " more on this click for help on the RUC-2 item. Note: Either" " RAOB or RUC-2 may be checked, but not both, as only one" " type can be used at a time." * 46 1180 5540 2900 5680 4710 2640 " This means no temperature changes due solely to transport of" " air via winds. This choice is acceptable when winds are very" " light and/or there are no significant temperature or dew point" " changes for a substantial distance upwind." "" " Even with this option, however, wind direction may still have" " some effect on temperature and humidity for two reasons. One" " is that, for sites on file, WXSIM has rough 'knowledge' of the" " distance and direction to the nearest large body of water, and" " will gradually modify the air mass according to the degree to" " which the wind is from that direction. This is most noticeable" " for coastal sites. The other is that WXSIM knows about normal" " conditions in the tropics and, if there is a component of wind" " from the direction of the equator, will slowly nudge temperatures" " towards those (usually warmer, but perhaps cooler if it is already" " very hot) conditions." "" " If you *know* that conditions upwind are truly very similar to" " those at your site, you can override most of the effect of the" " assumptions described above by choosing the 'Two Upwind" " Sites' option and clicking 'OK' without changing the default tem-" " peratures and dew points, which are simply those at your site." " Advection data via any of the three options, in fact, overrides" " most of these default wind-direction-dependent effects." "" * 47 580 7530 2700 6600 6690 3010 " This option allows you to input (or import) real time data for selected" " sites upwind from you, and is generally the best choice, assuming you" " have the appropriate data - temperature, dew point, wind speed, and sky" " condition. Only temperature and dew point are actually advected to your" " site, but wind speed and sky cover allow the program to better estimate" " the characteristics of the upwind air mass. Elevation and longitude" " differences as well as time of day are incorporated into this estimate." " Also, a smoothing routine (including averaging data from sites near each" " other) is used." "" " There are actually two different regional data routines. The first is an" " older one (retained for backwards compatibility with older site files) that" " groups upwind sites into 8 bins (N, NE, etc.), making certain assumptions" " to compensate for a site not being directly upwind. The second is a newer" " one that picks all known (to the program) sites within 22 degrees of the" " boundary layer wind direction and uses a world-wide climatology file and" " topographic data file to adjust the data; you can see the results of such" " adjustments by changes to the listing below. This method is used for any" " new custom sites, which have upper case site codes. It also allows import" " of surface data, which is still subject to user modification (in text boxes)" " and approval (the 'OK' button). You can tell if a site was found in your" " data file (which can have any name you choose) by an asterisk that will" " appear just to the left of the entry. NOTE: if data is missing for a station," " an 'M' should appear in the list and on the map for that item. You can" " estimate the missing value(s) yourself after clicking on that site in the list" " box, or let WXSIM make its own estimate(s), by simply clicking 'Use All'." " For buoy data, sky condition will default to mostly cloudy, which is appro-" " priate considering the small diurnal variations over water." "" " A relatively new feature is the ability to import NGM, GFS, and/or NAM MOS" " data (available only for the U.S.) to substitute for actual (and now outdated" " surface data after wind shifts. The data is interpolated (and averaged in" " the case of multiple sources) and treated just like real surface data, except" " that it is of course forecast data from other sources." * 48 1900 4780 2900 6230 3940 2870 " This is a simple option, for which you simply enter temperature and" " dew point for 2 points at distances (that you choose) upwind. While" " convenient, this does leave the user with the burden of compensating" " for elevation, sky condition, etc. and is therefore most useful when" " the upwind sites are at about the same elevation as yours and have" " wind and sky conditions similar to yours. It does allow for modelling" " of curved flow, assuming the user considers upwind streamlines when" " choosing and entering the two sites. This option is also available for" " sites not on file." "" " There is another situation in which this may be the best option:" " While 'Neutral' advection does not explicitly advect temperature or" " dew point, it does - to a degree depending on the site - gradually" " alter these with the wind from the tropics or if WXSIM knows of a body" " of water upwind. If you *know* that sites hundreds of miles upwind" " have basically the same temperature and dew point as your site, you" " may want to use this 'Two Upwind Sites' option, simply clicking 'OK' to" " the default values (which are the same as your temperature and dew" " point). This avoids WXSIM's 'second guessing' changes in maritime" " versus continental influence. You might want to experiment to see" " what works best." * 49 3780 4560 200 6300 3740 2830 " This option allows for quick and easy implementation of a wide range" " of common advection situations. The low numbers (1 to 2 on the" " scroll bar) establish gradients of temperature and dew point that trend" " towards upwind climatological normals. Higher numbers allow for" " increasingly marked frontal passages, with winds from a poleward" " direction considered cold for the season and site and those from the" " direction of the equator considered warm. This method is most useful" " when modifying winds during a run, since real time upwind data is not" " available. It can also be an interesting way to study the climatology" " of other sites, whether on file or not, since the descriptive terms" " like 'relatively diffuse' or 'strong' are relative to the site." " " " While you can set the frontal code to any value from 1 to 6.5, WXSIM" " provides a default value when you select this option. This will be 2" " ('gradual turn towards upwind normals') before the forecast run, but a" " new value will be calculated if wind shifts occur (manually or otherwise)" " during the run. The program uses the direction (veering or backing)" " and magnitude of the wind shift to make a very rough estimate how well" " defined a frontal passage (if any) may have occured." * 50 2800 3600 3000 6190 2760 2740 " This option generates smooth curves for the upwind temperature" " and dew point gradients. The curve is a linear combination of the" " 0.9 and 1.0 powers of distance upwind and is generated by a least" " squares regression on all the advection data. Such a curve is often" " more realistic than the 'connect the dots' straight-line fit. A second" " set of curves is also calculated, with an extra point with climatological" " normal temperatures at a great distance included to avoid bad" " extrapolations. Sometimes, upwind gradients which reverse sign (i.e." " warming, followed by a cold front) may be realistic, in which case the" " first set may be better. The 'Mono' (monotone) scroll bar allows these" " two sets to be mixed in various ratios, with a 50-50 mix as the default," " and higher numbers being more monotone. The 'goodness' of the fit" " is shown on the gradients plot by the root-mean-square (rms) error" " values for the actual advection data." * 51 2800 1840 3120 5700 1020 2600 " This option, available with one or more upwind sites being used," " generates a straight line segment ('connect the dots') fit for" " the upwind temperature and dew point gradients. While the real" " atmosphere usually has smoother gradients, this can be a good" " model for including frontal boundaries." * 52 1200 5360 2600 6260 4540 2940 " 'Advection' refers to the transport of conditions (here temperature" " and dew point) by the wind. In order to include this effect, WXSIM" " needs data representative of these conditions at points upwind from" " your site. There are five options here, as described by clicking on" " the blue captions at left (please read about all of them)." "" " This transport actually occurs at all levels of the atmosphere, but" " advection near the surface is usually the most important level for" " forecasting conditions at the surface, and that is what WXSIM uses." " A crucial component of this simulation is the wind speed, as a small" " difference here can greatly affect the timing and extent of changes" " caused by advection. For this reason it is important to use properly" " measured wind speeds, in open areas at least 20 feet (6 meters) above" " the ground. For some custom sites (such as official NWS sites)," " consideration of climatological wind data will have been given, so" " that existing anemometers should give appropriate values. A lot of" " empirical work has gone into making advection an appropriate function" " of surface wind speed. Of course direction is crucial, too, so care" " should be taken to use a wind direction averaged over several minutes." " Winds higher up are taken into account in less direct ways, such as" " assumptions about how temperatures higher up relate to those near the" " ground and, especially, the ability to use output from large models" " (such as NAM and NGM) to modify WXSIM's upper air data." * 53 2780 3040 1500 5340 2200 2440 " This feature allows you to modify the program's 'educated" " guess' sounding. Examine the temperatures and/or the plot" " to decide whether such an adjustment is necessary. If you" " have used imported FOUS data, the gray plot on the right" " may be a useful guide. Clicking in the 'Multi Layer' bar" " will raise or lower level 2's temperature by 1 degree C," " while clicking on the ends will fine tune it be 0.1 degree" " per click. Levels 1 and 3 will change 0.75 as much, level 4" " by 0.5 as much, and level 5 by only 0.25 as much, which is" " consistent with the much smaller variation of temperature" " at high altitudes. To adjust a layer individually, use the" " 'Single Layer' scroll bars." * 54 1680 4590 1500 5200 3760 2280 " This gives you a chance to modify the program's assumed" " level 1 and 2 dew points, which are based on such data" " as surface dew point and cloud cover. If 'Auto' is" " checked, the program will continue to use its own, con-" " tinually recalculated values. If you wish to put in" " your own values, they will stay fixed, except for the" " fact that they cannot exceed the temperature in that" " level. A useful time to put in actual values is when" " you are using the auto stratus and/or auto cumulus rou-" " tines and advection is minimal. You also have a chance" " here to enable or disable these routines. If you fix a" " dew point (they are considered separately in this regard)," " you can still change this later with interrupt 'y'." "" " NOTE: As soon as you click 'Fix', the dew point listed in" " the 'Fix at' box will revert to its default value; however," " the value you entered (as long as it didn't exceed the" " temperature) will be shown in the data grid to the left and" " properly plotted on the sounding below." * 55 700 4360 300 5660 3560 2500 " 'Lifted index' is a commonly used indicator of atmospheric" " instability. It is basically the difference between the" " ambient temperature at the 500 millibar level and that of" " an air parcel lifted from the surface. It is actually the" " 500 mb temperature minus the parcel's temperature, so if it" " is negative, the parcel is warmer and, like a hot air balloon," " will keep rising. This is an 'unstable' atmosphere and can" " lead to thunderstorm activity. There are other factors, but" " LI is one of the most useful simple indices. This version" " uses a combination of actual surface temperature and dew point" " and values extrapolated down from level 1. This approach is" " especially useful for morning soundings, when inversions near" " the surface can otherwise skew the results. Here is a key:" "" " +3 to +1 Showers possible, thunderstorms unlikely or weak" " 0 to -2 Thunderstorms possible (could be severe in winter)" " -3 to -5 Thunderstorms likely, some could be heavy or severe" " < -5 Severe thunderstorms likely" * 56 1620 3440 300 5660 2600 2460 " 'Lifting condensation level' is the height at which a parcel" " of air being lifted (either by buoyancy or other external" " forces) will cool adiabatically to its dew point and form a" " cloud. This determines the height of the base of convective" " clouds, if they form. Commonly, in the morning, this height" " will be quite low and is not particularly meaningful as clouds" " are not likely to be forming from air lifted from the surface," " unless it is blowing up the side of a mountain. If the auto" " cumulus routine indicates cloud development, though, as may" " happen by afternoon during the warm season, the LCL is a" " fairly reliable indicator of the base height of these clouds." " Here, LCL is shown in three ways: height above surface (in feet" " or meters), height above sea level, and pressure level in mb." * 57 2800 2440 1500 5180 1600 2400 " This is the last time at which you 'saved' a sounding plot." " If you 'Reset Previous', the program will remember the plot" " for the current model time so that you can view it later" " by clicking 'View Previous'. This gives you a way to see" " how the upper air profile has evolved since you last 'reset" " previous'. This old sounding will appear in darker shades" " of red and blue than the current one. The last reset time" " is indicated under 'Prev Time'." * 58 2420 1420 2200 4340 600 1900 " This is the current azimuth (direction) of the sun," " in degrees to the right of due north, i.e. N = 0," " E = 90, SW = 225, etc." * 59 2420 1420 2200 4260 600 1860 " This is the azimuth (direction) of the sun at" " SUNRISE, in degrees to the right of due north," " i.e. N = 0, E = 90, SW = 225, etc." * 60 2200 2620 2900 4060 1800 1760 " Wind Chill Factor:" " This is a measure of the combined heat-loss" " effects of low temperature and wind on the" " skin. It is not an actual temperature, but" " is given as the temperature that, with a wind" " of only about 3 knots (walking speed), would" " feel the same as the current conditions. The" " algorithm used here is the NEW (late 2001)" " one from the U.S. National Weather Service." * 61 2200 3040 2900 4360 2200 1960 " Heat Index:" " This is a measure of the combined heat-stress" " effects of high temperature and humidity on" " humans. It is not an actual temperature, but" " is given as the temperature that, with a modest" " humidity (corresponding to a dew point of about" " 56F or 13C), would feel the same as the current" " conditions. Here this value is computed using" " an algorithm developed by the author to match" " the U.S. National Weather Service's official" " chart, but is NOT the NWS's mathematical model" " of their chart." * 62 180 6600 800 5750 5780 2550 " Soundings presented here are based on TTAA data for up to 3" " sites, as specified in your site's custom data file. If the data for" " one of the station synoptic codes is blank, this means no TTAA" " data was found for that site. The weighted averages should" " best represent your actual location. Note that for each site," " the bottom entry refers to the surface. If higher pressures are" " listed above this, they are extrapolations under ground and do" " not represent actual conditions in the atmosphere." "" " The data at lower right consist of standard thicknesses data," " temperatures from various levels extrapolated adiabatically to" " the surface, and three stability indices. More information is" " available by clicking on the appropriate blue caption." "" " Note that RAOB sounding data will not be directly used during" " WXSIM's forecast run, but you do have an opportunity to" " incorporate the information by tailoring the sounding on the" " upper air data form to match the sounding, which will appear" " as a pair of black sounding lines on the graph on that form." " Caution is advised, however, because upper air conditions vary" " both from night to day and because of large scale changes, so" " an old (more than a few hours) sounding may be worse than no" " sounding at all." "" " If the upper wind directions shown match current conditions well," " you may want to click the 'Set Upper Winds' button. This sets" " the upper wind directions on the Data Entry form to the RAOB" " values and can improve the initial temperatures, especially if" " winds are strong and WXSIM's 5 pressure levels are close to the" " mandatory RAOB ones." * 63 1800 1720 1400 5860 900 2540 " These extrapolated temperatures are mainly useful in the warm" " season, when mixing may reach 850 mb or higher during afternoon" " heating, when, with full sunshine, these temperatures may actually" " be reached. If these temperatures are reached, convection is" " also a possibility." * 64 1000 4460 1200 6640 3650 3100 " The K Index is a commonly used stability index. It is determined by" "" " K = T1 + TD1 + TD2 - T2 - T3" "" " where T1, T2, and T3 are the temperatures (Celsius) at the 850, 700, and" " 500 mb levels, respectively and TD1 and TD2 are the 850 and 700 mb" " dew points (Celsius). The following chart is a rough guide to its use:" "" " K Index Thunderstorm Probability" "" " 15-20 Less than 20%" " 21-25 20-39%" " 26-30 40-59%" " 31-35 60-79%" " 36-40 80-89%" " >40 90% or greater" "" " (Adapted from Accu-Weather's Accu-Data (TM) User's Manual, edition 3.0.)" * 65 1000 4400 1200 6840 3580 3150 " The Total Totals Index is a commonly used stability index. It is determined by" "" " TT = T1 + TD1 - 2 x T3" "" " where T1 and T3 are the temperatures (Celsius) at the 850 and 500 mb levels," " respectively and TD1 is the 850 mb dew point (Celsius). The following chart" " is a rough guide to its use:" "" " TT Index Thunderstorm Activity" "" " 44 Spotty, usually weak thundershowers" " 46 Spotty, usually moderate thundershowers" " 48 Usually heavy thundershowers" " 50 Usually thunderstorms, hail possible" " 52 Severe thunderstorms, tornado possible" " 56 Severe thunderstorms, tornados likely" "" " (Adapted from Accu-Weather's Accu-Data (TM) User's Manual, edition 3.0.)" * 66 5040 3370 6700 4320 2560 1900 " This is 'visible sky transmittance', meaning the" " average amount of solar radiation reaching the" " ground (including both direct and diffuse light)," " expressed as a percentage of what it would be" " under very clear skies. It takes into account" " fractional cloud coverage, opacity of clouds," " haze, and fog, all as entered by the user. It is" " actually intended to represent all 'shortwave'" " radiation, which includes some infrared and" " ultraviolet light near the visible spectrum, but" " is therefore mainly 'visible'. Values given at" " night may be considered percentage of possible" " starlight or moonlight making it to the surface." * 67 1700 6500 3510 6320 5680 2860 " The 'Use FOUS' routine allows WXSIM to 'blend in' many aspects of" " imported NAM and NGM model data. Use of upper air temperatures," " boundary layer temperature, sea level pressure, cloud cover, relative" " humidities (from which clouds are derived), precipitation, and wind" " data are supported. You can specify the 'weight' you wish WXSIM to" " give the first three items, ranging from 0 (totally ignoring them) to 100" " (near-rigid adherence). The default values shown are a compromise," " generally giving WXSIM more weight to maintain its integrity as a" " model. Note that upper level temperatures are weighted more since the" " 'big' models usually handle them better, while boundary layer tempera-" " ture is left mainly to WXSIM since that is WXSIM's 'specialty'. The only" " pressure modelling done by WXSIM is an empirical treatment of diurnal" " variations, so the default gives FOUS a considerable effect. The" " internal weighting scheme actually involves a 'pull' towards FOUS has" " a characteristic 'half life', shown in hours at right." " " " For clouds, level 2 humidity, wind (speed, with direction only used in" " the form of a warning if it deviates from current boundary layer wind" " direction by more than 36 degrees), and precipitation, check boxes are" " provided. The 'half lives' used here are very short, so that the routine" " is heavily in charge of these items - though you can sway them with" " frequent program interrupts. The cloud routine affects levels 2,3, and" " 5 only; you have the option of rapidly (within a few hours' model time) of" " phasing out any entered level 1 and 4 clouds by checking the 'Clearing" " trend...' box. Precipitation can be specified in the form of 30 minute" " showers starting every 1.5 hours (the timing of this is complicated by the" " shower routine on the Interrupt Planner). Wind speed will still show" " much of WXSIM's diurnal variation, as the program modifies the FOUS" " boundary layer values for use at the surface." * 68 3500 1640 1120 7400 820 3400 " Higher elevation sites are generally cooler than lower ones, generally by about 2.5" " degrees Fahrenheit per 1000 feet (about 4.5 degrees Celsius per km). This assumes that" " the site is on a wide area of similar elevation, rather than on an isolated peak or in" " a canyon. Elevations of more than 14000 feet (4266 meters) will not be accepted." * 69 3600 2840 1120 7700 2000 3600 " Areas near the centers of large continents generally experience extremes of temperature" " relative to coastal locations, and because of prevailing westerly winds, areas in the" " eastern part (but not on the coast) of continents may also see such extremes. Small" " islands and west coasts of continents have much more moderate conditions since water is" " quite slow to change temperature. Generally, on this scale of 0 = totally maritime to" " 100 = totally continental, a typical mid-ocean island rates 15 or less, a continental west" " coast about 30-40, an east coast about 50-60, and the interior of large continents 70 or" " more, with only east-central Asia reaching 100. The estimated value, from a world-wide" " 5x5 degree grid, should be quite accurate except in some coastal regions; you have to" " set the value yourself, but should stay close to this recommendation." * 70 4380 1800 1120 7600 990 3400 " Time zones are based on specific longitude lines, usually (but not always!) the multiple" " of 15 closest to the site's actual longitude. Simply put, this longitude is 15 times the" " number of hours from Greenwich - west if behind GMT, east if ahead. In a few places, a" " 30 minute difference from adjacent time zones may be in use, requiring a 7.5 degree" " difference in this time-zone longitude." * 71 4480 2220 250 9150 1400 4270 " Diurnal and seasonal temperature ranges depend to some extent on the type of surface. Dry, sandy soil" " with little vegetation allows for larger temperature ranges and also is associated with smaller amounts of" " transpiration and evaporation of water vapor into the air as compared with heavily vegetated surfaces or" " large areas of water. Your input value should be descriptive of the predominant surface type in the area," " especially a short distance upwind from your site. The estimated value is derived from the same data as" " the continentality (above), but is not as accurate due to the rough scale of the grid and other factors." " Often, west coasts are drier than east coasts with the same degree of continental influence. Your" " estimate here is probably better than WXSIM's." * 72 2100 2600 960 5060 1780 2240 " This is climatological data consisting of the average" " of all 12 monthly mean temperatures, which are, in turn" " averages of daily means (averages of daily max and min)." " The default value listed is interpolated from a world-" " wide data file with grid points every 5 degrees of latitude" " and longitude and adjusted for elevation. It should be" " quite accurate except near some coastlines (mainly west" " coasts near cold ocean currents) and in some mountain" " regions. You may change this value if you have more re-" " liable, site-specific data." * 73 2300 2420 960 5060 1600 2240 " This climatological data consists of the normal daily" " mean (average of max and min) temperature for the date." " The default value listed is interpolated from a world-" " wide data file with grid points every 5 degrees of latitude" " and longitude and adjusted for elevation. It should be" " quite accurate except near some coastlines (mainly west" " coasts near cold ocean currents) and in some mountain" " regions. You may change this value if you have more re-" " liable, site-specific data." * 74 2300 2420 960 5060 1600 2240 " This climatological data consists of the normal daily" " mean dew point (average 24 hourly values) for the date." " The default value listed is interpolated from a world-" " wide data file with grid points every 5 degrees of latitude" " and longitude and adjusted for elevation. It should be" " quite accurate except near some coastlines (mainly west" " coasts near cold ocean currents) and in some mountain" " regions. You may change this value if you have more re-" " liable, site-specific data." * 75 1680 3040 1140 4900 2240 2240 " This climatological data consists of the approximate" " surface temperature (for the date) that a large body" " of water near the site has (or likely would have if it" " existed). It corresponds fairly closely to the normal" " soil temperature a few inches (about 10 cm) deep and" " is also used in estimating upper air temperatures. It is" " actually a parameter used in obtaining a good fit to" " climatology for custom (on-file) sites and does not" " always match the above definitions exactly. It is often" " best to simply accept the default value, but for coastal" " sites it is suggested that you input actual sea surface" " temperature here." * 76 1050 6340 200 6760 5520 3020 " This data retrieval program allows you to view both text and graphs of" " forecast data you've saved using WXSIM. Thses files have the extension" " .WXF and may be saved in the directory of your choice." " " " First, select your file. Then select the starting day (i.e. a choice of '2'" " will start data retrieval at 12:00 AM of the second day of saved data) and" " the number of days of data you want retrieved. Next, check up to 5 boxes" " under 'Temperatures and Thickness' and up to 5 under 'Other Data' to select" " the data types to be displayed. You can select more items, with the extras" " appearing only in lastret.txt. Note that you may also use daylight savings" " time (whether you selected it at run time or not) and have lots of choice of" " units." " " " Both text and plotted data can be printed out after being displayed. Note" " that when viewing the graphs, multiple vertical axis scales are color coded" " to pack a lot of information into these graphs and still make them readable." " ALSO, you can use the mouse cursor on the plot itself to select a time and" " then click to display an upper air sounding with selected surface data, and" " then pan forwards or backwards in time using the right or left arrow buttons" " on the form. Moving the mouse over the sounding displays its position" " on the sounding. Also note the 'Compare to Actuals' button, to see how" " previous forecasts compare to actual home weather station data." " " " When you select text as the display mode, a text file will automatically be" " generated. Its name is lastret.txt and it will be placed in the directory" " indicated below this 'Help' caption. If you want screen shots of the" " graphics, you can check 'Save Bitmap' on the Plots form, and additionally " " you can save soundings using 'Inc Soundings'." * 77 350 8260 500 5060 7440 2240 " Here you can select up to 5 temperature-related items," " plus a 'thickness' (between given pressure levels) for" " text or graphical display. You can select a total of 15," " 5 of them being displayed, while all 15 will be written" " to the lastret.txt file. Freezing level, above either" " sea level or ground level, is grouped with thicknesses." " All temperatures will be shown using the units (F or C)" " of your choice, with thickness in either meters or feet." " All except level 1, 850 mb, and boundary layer refer to" " values about 6 feet (1.8 meters) above the surface." " " " Temperature - properly sheltered value about 6 feet (1.8" " meters) above ground (preferably grass)." " Dew Point - temperature at which air would be saturated." " Wet Bulb - temperature of wet wick of psychrometer." " Wind Chill - 'apparent temperature' considering wind." " Heat Index - 'apparent temperature' considering humidity." " Humidex - Canadian alternative to Heat Index." " Level 1 Temperature - usually ABOUT 1640-1840 feet" " (500-560 meters) above the surface." " 850 mb Temperature - at 850 millibar pressure level." " Boundary Layer Temperature - mean for lowest 35 mb." " Temperature Advection - change (per hour) in tempera-" " ture due solely to transport of air (wind)." " Dew Point Advection - change (per hour) in dew point" " due solely to transport of air (wind)." " Valley Temperature - temperature likely in relative low" " elevation spots (~100 ft or 30 m below local mean)," " most significant on clear, calm nights with 'cold air" " drainage'." " Hill Temperature - temperature likely in relative high" " elevation spots (~100 ft or 30 m above local mean)," " most significant on clear, calm nights with temperature" " inversions." " Max w/Variations - curve whose peak should be max" " temp for the day, considering short-term fluctuations." " Min w/Variations - curve whose valley should be min" " temp for the day, considering short-term fluctuations." * 78 450 8050 400 5520 7220 2460 " Here you can select up to 5 items for text or graphical display." " You can select a total of 15, 5 of them being displayed, while" " all 15 will be written to the lastret.txt file. Note that some of" " the units depend on units choices made under 'Temperatures" " and Thickness'." " " " Wind Direction - direction wind is blowing from." " Wind Speed - value about 20 ft (6 m) above surface in area" " away from trees or buildings." " Gust - highest wind speed sustained for 3 seconds, during" " surrounding 1 minute, 10 minutes, 1 hour, or 6 hours." " Sun Altitude - center above horizon in degrees (ignoring" " refraction by atmosphere)." " %Visible Sky Trans. - 'global' visible light reaching surface as" " a percentage of very clear day value." " % Total Sky Cover - percent of sky (as seen from ground)" " containing clouds at any level, of any opacity." " % Sky Cover (Lev 1,2) - percent of sky (as seen from ground)" " containing clouds at levels 1 and 2 only, of any opacity." " Solar Irradiance - global visible on horizontal surface (in" " Watts per square meter)." " Ultraviolet Index - global UV (~280-390 nm) on horizontal" " surface (in units of ~25 mW per square meter)." " Horizontal Visibility - maximum distance at which surface" " features can be seen from the ground." " Sea Level Pressure - barometer reading reduced to sea level." " % Relative Humidity - vapor pressure as percentage of" " saturated value at current temperature." " Precip Chance/Hour - chance of measurable precipitation" " occurring within 30 minutes either side of present time" " (experimental/questionable accuracy)." " Precipitation Intensity - rate of liquid equivalent fall per hour." " Precipitation Total - accumulated liquid equivalent since the" " beginning of the forecast run." " Snow/Ice Depth - current average depth on ground." " Lifting Cond. Level - height above ground at which clouds" " could form from air lifted from surface." * 79 2080 3180 1140 5010 2370 2220 " If this box is checked, the advection profiles shown" " when you click 'OK' will be stored in memory in case" " you want to use them again without having to re-enter" " the advection data on which they are based. To re-use" " this data on your next run, use the 'Repeat' option" " after the current run and then on the next run, just" " click 'Use Previous' when this form reappears. The type" " of advection method originally used will be indicated" " in red. You will again have a choice of a curved or a" " straight fit, without changing the underlying data." " NOTE: This 'Use Previous' option becomes meaningless" " you significantly alter initial data, including the" " calibration run." * 80 1240 2620 920 4960 1800 2140 " If this box is checked, the latest upper air adjustments" " (to temperature and dew point, resulting from '1-Click," " FOUS, RAOB, fixed dew point, or other manual changes" " made earlier) will be stored in memory in case you want" " to use them again without re-entering next time. To re-" " use this data on your next run, use the 'Repeat' option" " after the current run and then on the next run, click" " 'Use Prev' when this form reappears. You may also re-" " fine these settings in the usual way if desired." * 81 70 6680 3200 6100 5870 2900 " This option allows you to import TTAA format analysis data for" " the RUC-2 (Rapid Update Cycle) or MAPS models, which are run" " hourly for much of North America. Since this data is based largely" " on aircraft reports, it fills much of the gap between RAOB" " observations, both temporally amd spatially." "" " WXSIM can use this data in the same way as it does actual TTAA" " RAOB data, displaying it as text and on the upper air sounding plot" " as temperature and dew point curves towards which the user can" " 'click' WXSIM's initial upper air profile (see the RAOB help item)." "" " To make use of this data, the RUC-2 check box must be checked," " which will un-check the RAOB box, since only one or the other" " of these sources can be used. Also, the five-digit ID for the station" " (i.e. closest airport) of your choice must be entered in the text box." "" " This data is currently (April, 2009) provided on the Internet" " courtesy NOAA's Forecast Systems Laboratory at:" "" " http://rucsoundings.noaa.gov/gifs/" "" " Enter the airport site closest to your station, obtain the analysis" " sounding plot for the time nearest WXSIM's initial run time, and then" " click for the FAA604 format data. Save under a file name of your" " choice, then select this file for import into WXSIM." "" " NOTES: This data actually represents conditions at the nearest" " model grid point, and uses the model terrain for surface elevation." " WXSIM makes allowances for any altitude difference and also cal-" " culates an approximate 1000 millibar height if this TTAA data omits it." * 82 800 5760 300 6420 4940 2880 " The '1-Click', FOUS and RAOB 'Mix' buttons allow you to make quick" " adjustments to WXSIM's upper air profile. The '1-Click' is often the most" " convenient of these, and will be described last." "" " Each click of the FOUS button will take the current temperature and dew" " point profiles halfway to the FOUS-based sounding. Likewise, the RAOB" " button takes the profiles halfway to the RAOB sounding." "" " How many such clicks to do depends on how much you trust WXSIM's" " native profiles versus the FOUS and RAOB ones. If the FOUS or RAOB" " data are more than several hours old, a single click giving WXSIM equal" " weight might be appropriate. If the FOUS or RAOB data are nearly real-" " time, though, you could give them more (i.e. 3 clicks, or 7/8 weight)." "" " The '1-Click' option is a more recent addition to the program which takes" " much of the guesswork out of adjusting the profiles. It automatically" " determines reasonable weightings of the FOUS and RAOB data, based" " on how many hours old each are, and effectively 'clicks' the FOUS and" " RAOB buttons for you. Another big advantage is that, in the case of" " RAOB data, it automatically factors in expected diurnal changes to the" " RAOB profile so that, for instance, a morning sounding is still relevant" " that afternoon (assuming weak advection). In such a case, you may" " notice the lower level temperatures (red line) departing from the RAOB" " data (right black line). NOTE: Subsequent clicking of the RAOB button" " will pull WXSIM's sounding towards the original (no diurnal correction)" " profile." * 83 2800 3980 980 7540 3160 3420 " This feature lets you cull through large files of surface (METAR or SYNOPtic) or upper" " air (RAOB) data to create new files consisting only of data relevant to your site." " For RAOB data, only TTAA data up through 300 mb for your three RAOB sites and" " most recently used RUC-2 site will be written to the new file. Surface data selected " " includes the on-file site and all advection sites for which data is found." "" " To use this feature, select the source file, which appears in the text box at left. The" " default destination file is named WXDATA.TEXT, though you can change this. If you" " leave the same name in this box while culling for the various types of data, all types" " of data will be placed in the same file. You can also append other data (such as" " FOUS) by using the 'Other' option. If 'Remove SPECI reports' (applicable to METAR" " only) is checked, special between-hours reports will be excluded. This helps keep" " advection data synchronous." "" " The culling process actually takes longer than using the source file itself, and is" " therefore useful mainly if you will be using the same data several times or simply wish" " to append smaller files." * 84 30 6780 480 8660 5940 7960 " The graphs below will be plotted if you import NGM or NAM FOUS model data for your site. Precise" " definitions of some of the variables may require further inquiry and in fact may be defined slightly" " differently depending on the model, but the following definitions are fairly accurate and largely" " common to both models. First of all, 'boundary layer' refers to average conditions in the lowest 35" " millibars or so (about 1000 feet or 300 meters) of the atmosphere. Other pressure levels specified" " below are based on a surface pressure of 1000 mb; for a surface pressure of 900 mb, adjust by" " multiplying the values given by 0.9, for example. The time scale (horizontal) starts with the model" " initialization time (either 00Z or 12Z). The vertical black line shows WXSIM's initialization time." " The graphs are useful mainly for planning your WXSIM run, but some of the data can be factored in" " with WXSIM's forecast (see the NAM and NGM import check box help). Graph by graph, we have:" " " " Top graph: R1, R2, and R3 are average relative humidities in the boundary layer, and thick layers" " centered around about 718 and 325 mb, respectively (roughly 10,000 and 28,000 ft above the" " surface for most sites). While many other factors are involved, R2 and R3 values of over 70% are" " likely to be associated with some cloudiness in those layers. The 6 hour precipitation numbers" " refer to inches fallen in the *preceding* 6 hours." " " " 2nd graph: '700 VV' refers to the 'vertical velocity' at the 700 mb level, in microbars per second." " Rising air (values above the 'stable/unstable line) tends to favor condensation. 'LI' is the" " 'Lifted Index'; if this is negative (*above* the line), convection (i.e. thunderstorms) is favored." " " " 3rd graph: SLP is sea level pressure in millibars. DIR is boundary layer wind direction (note the" " W, S, and E). SPD is the boundary layer wind speed in knots, though surface winds tend to be" " only about 70% of this, depending on the site." " " " Bottom graph: T1 is the boundary layer temperature (Celsius), similar to that at the surface, but with" " less diurnal range. T3 and T5 are average temperatures in layers centered near 897 and 785 mb," " respectively, about 2000 and 3500 feet above the surface. The 1000-500 mb thickness is in" " meters and is related to the average temperature in the lowest 18,000 feet or so. A value of 5400" " meters suggests average temperatures of freezing or below and is often used as a rough 'critical" " thickness' for rain (>5400) versus snow (<5400). The 'rain/snow' line shown doubles as the" " 0 C temperature line, to aid in precipitation-type decisions (though WXSIM makes its own)." * 85 160 6100 1500 6400 5290 4840 " This is a forecast of afternoon maximum temperature based on the level" " 2-to-surface thickness (the lowest 135 mb or so). It is similar in many" " ways to various 'full-sun thickness' schemes, but more flexible in that" " it takes advantage of some of WXSIM's data and modelling abilities. In" " particular, the values output are essentially NOT dependent on the time" " of day. In other words, WXSIM knows where in the diurnal variation this" " low-level thickness is at any time of day, so it is not necessary to be" " restricted to 12Z soundings. Also, MANY factors are included in the" " calculation - such as elevation, latitude, time of year, humidity, cloud" " cover, haze, snow cover, and short-term temperature fluctuations - so" " that virtually no 'second guessing' or adjustments are needed. These" " built-in adjustments are applied to a basic dry-adiabatic extrapolation" " to the surface. Notice that values are given for CL, SC, BK, an OV sky" " conditions. These refer to average 'opaque' cloud cover (usually low or" " mid level) expected during the late morning through afternoon. CL(ear)" " means few if any clouds, SC(attered) about 30% coverage, BK (broken)" " about 75%, and OV(ercast) close to 100%. High, thin, clouds have much" " less effect. A high, thin overcast would rate as SC, or BK at most." " " " There are serious limitations to this method, however. The estimates" " will not be reliable if significant temperature advection occurs. Another" " problem is temperature inversions, especially in winter. If the low-" " level atmosphere is poorly mixed (common in winter), the values may be" " too high, even with the built-in, smoothly varying seasonal dependence." " " " You can consult this routine at any point during the forecast by pressing" " the 'y' key interrupt. Notice that the default units are Celsius, but" " you can quickly click the Fahrenheit option if desired." * 86 520 6420 100 5600 5590 2530 " This shows possible upwind advection sites within 22 degrees" " of the current base mean boundary layer wind direction - which" " may be a bit different from the actual surface direction due" " to surface friction and/or sea breeze effects - and is shown" " as a long dotted purple line starting from the home site. You" " may also see a curve here if you are using cyclonic or anti-" " cyclonic flow (see the help for those items). The sites" " are shown as small gray circles. North is up, and the first" " large circle has a radius of 250 miles (about 400 km) from the" " home site. If you click on a site (in the list box - not on" " the map), the site will be colored red indicating that you have" " selected it. If you actually enter data and use the site, it" " will turn green." " " " If you import surface data, station models will be plotted for" " sites for which data is found. Temperature (in red, in the" " units you are using) and dew point (blue) will appear to the" " left of the circle, which will be white if skies are clear or" " nearly so, light gray if scattered clouds are present, dark gray" " for broken clouds, black for overcast, or blue if precipitation" " is occurring. Buoy data are automatically plotted as overcast" " to simulate their small diurnal temperature range. Red arrows" " show wind directions, with speed indicated by the length of" " the arrow. The scale of the plot is determined by the choice" " of scale on the gradient plot below. You will also be shown" " a weighted vector average of surface wind speed and direction" " for the upwind sites found, together with your home site. In" " some cases you may want to modify your input wind direction to" " take this into consideration." * 87 1760 6320 1460 9060 5500 4190 " This form allows you to plan changes in cloud cover, wind, pressure, precipitation, and upper air" " temperatures so that they will be automatically executed during the run. You may enter changes for" " any or all of the items, use model data ('Use Model Data from READY or GFS') you've already imported," " or just leave it blank. You can even manually alter the READY data if you have reason to." "" " To enter changes, click an option and then position the mouse on the graph at the desired time and" " variable value (as seen under 'Current Mouse Position'), and click. An appropriate interpolation from" " the last entered value (or initial value from data entry, for the first click) will be plotted. Up to 62 clicks" " for each variable are allowed (except 61 for abrupt changes). There are three types of interpolations:" "" " Cloud cover in any of the 5 layers will plot linearly. Wind speed, sea level pressure, 1000-500 mb" " thickness (related to average temperature in the lower half of the atmosphere), and 850 mb (or 700 mb" " for sites above 2500 feet) temperatures will plot as diurnally varying curves. These items depend on" " cloud cover, so you should enter clouds first. Precipitation and wind direction are treated as abrupt" " changes, with steady values in between, so these plot like 'stair steps'. Note: the thickness and" " 850 or 700 mb temperature scales can be changed under 'Customize' on the Data Entry form." "" " If you are employing NGM/NAM FOUS data, this data will in most cases be averaged with your planned" " data for use during the forecast. FOUS does not control level 1 and 4 clouds, and the planned data will" " always have the 'last word' on wind direction. With pressure and upper air temperatures, FOUS data is" " more heavily weighted if high 'effects' (close to 100%) are chosen on the 'FOUS Usage Setup' form." "" " If the 'Save for next run' box is checked, the current data (except for initial values) will be saved for" " the next run, though you may add more changes at that time. 'Clear All' voids all but the start-time data." " 'Clear Selected' clears only the variable whose option button is selected. 'Clear Last' clears the last" " clicked value of the selected variable, and may be used repeatedly to clear earlier values. For help on" " 'File Save' or 'File Recall', click either button. You can easily modify existing data by clicking on the" " graph, in spite of the existing plots; the plots will bend or adjust to accommodate the new data." * 88 820 2080 1775 6000 1260 2650 " You can save planned changes for later recall with the 'File Save'" " option, and recall them with 'File Recall'. To save a file, just click" " 'File Save' on the planning form, select the desired drive and direc-" " tory on the current form, and type a name in the text box over the" " default 'lastplan'. To recall data from a file, locate the file in the" " drive, directory, and file boxes and click on it. In either case, click" " OK (or 'Cancel' to abort)." * 89 400 7520 270 9220 6680 4240 " This option allows you to import a variety of model output, in text meteogram form, from NOAA's" " 'READY' site, at http://www.arl.noaa.gov/ready/cmet.html. If imported into WXSIM, this data will be" " be displayed graphically on the Interrupt Planner, where it can be used 'as is' or modified, if you like." "" " The model data that WXSIM can use are total cloud cover (which is split among levels 2,3, and 5 on the" " planner, considering overlap), sea-level pressure, wind speed (either directly or from U and V compo-" " nents), wind direction (from U and V components), 850 mb (or 700 mb, for sites above 2500 feet) tem-" " perature, 1000-500 mb thickness, and accumulated (over 3, 6, or 12 hours, depending on the model)" " precipitation." "" " To obtain this data, get on the internet and go to the URL given above. Find 'Forecast Model Graphics'" " and, under that, 'Forecast Meteograms'. Choose a model; the GFS (was AVN) has the advantage of data" " being available for the whole world, but others may supply greater accuracy or finer detail. After selec-" " ting a model, hit 'Go'. On the page that now appears, enter your site, by name, location, or from a map." " On the next page, enter the forecast duration desired (as long as it's no more than your planned WXSIM" " run). You can choose 'Text Only', or look at graphics first and then get the text." "" " You can choose either of the default selections, or define your own. A small obstacle is that not quite" " all of the items that WXSIM can use can be displayed at once; if you want more than five items, you'll" " need to make two requests and append the files together, either by saving them separately and combi-" " ning later using WXSIM's 'Cull/Append' feature, or (perhaps quicker) by copying and pasting into a text" " file (i.e. in Notepad), perhaps one in which you are putting METAR, RAOB, and/or FOUS data." "" " You can also get a 'consensus' of models by including more than one in your file. WXSIM will average" " any data items that it finds in more than one model. The averaging is done successively, so that the" " most recently found values are equally weighted with the average so far. The starting times do not have" " to be the same, but of course any older data is likely less reliable. One restriction is that the output" " intervals must be the same; you cannot mix 3-hour interval data with 6-hour interval data." "" " A powerful and convenient alternative to READY data is GFS 180 hour, 3 hourly model data culled from" " GRIB files by Chris McMahon. To get access to such data for your site, you must be a registered WXSIM" " and WXSIMATE user. Just send a request to me (Tom Ehrensperger) to set your site up on Chris's system." " There is no charge for this service. The data is site specific, contains more data points than READY, and" " is retrieved automatically by WXSIMATE, with no need for a manual visit to any site. See section XI in" " the manual for more information." * 90 3620 3000 200 6160 2180 2780 " This option allows you to directly specify surface advection of both" " temperature and dew point by simple mouse clicks on the graph at" " lower right. The horizontal axis is neutral advection; above is warm" " and below is cold. First specify the temperature profile by clicking" " the desired relative temperatures and distance upwind. After you" " are finished with the temperature clicks, click the 'dp' check box and" " click the corresponding relative dew points. Note that you now have" " no choice of distances, as these points will correspond to those you" " entered for temperature, in the order you entered them, regardless of" " the horizontal position of the mouse when you click. If you decide to" " start over, just click 'Neutral (none)', then 'Direct Click' and try again." * 91 2200 2620 2900 4170 1800 1790 " The Showalter Index is another stability index," " really the same as lifted index, but with the" " parcel's starting level at 850 millibars instead" " of the surface (or near surface). This makes it" " less sensitive to diurnal variations and also" " enables it to 'see' elevated instability even if" " the surface layer is more stable. Showers or" " thunderstorms are possible with values of +3," " but negative values may indicate possible" " severe weather." * 92 2100 2860 3100 4450 2010 1960 " The KO Index is a stability index tailored for use" " in cool, moist climates such as Northwestern" " Europe. It is defined as:" " " " (e5 + e7)/2 - (e8 + e0)/2" " " " where the e's are the equivalent potential tem-" " peratures at 500, 700, 850, and 1000 mb. Values" " over +6 suggest little if any shower activity, while" " values <1 imply probable thunderstorms." * 93 2100 3030 2900 4530 2200 1960 " The Boyden Index is a stability index tailored for" " use in cool, moist climates such as Northwestern" " Europe. It is defined as:" " " " (h7 - h0)/10 - t7 - 200" " " " where (h7-h0) is the thickness of the 1000-700 mb" " layer in meters and t7 is the temperature at 700 mb" " in Celsius. It is especially useful with cloudy con-" " ditions near fronts, when values of 94 or greater" " imply probable thunderstorms." * 94 2670 5690 200 9350 4900 4300 " When using the Regional Data advection option, you can model curved flow by adjusting the 'Cyclonic/" " Anticylonic' scroll bar (cyclonic flow is counterclockwise in the Northern Hemisphere). The airstream will" " be represented by the dotted purple curve on the site map. If you have imported METAR or synoptic data," " surface winds will be shown as arrows on the map, and the idea is to try to match the suggested flow" " (actually the program wants to match the mean boundary layer flow, which may be several degrees different" " from the indicated surface flow). The closeness of this fit is indicated by a distance-weighted mean" " velocity component along the direction of the assumed curve, shown as 'Spd', and as a percentage (%) of" " the maximum possible. The upwind distance used in the program is the distance along the curve." " " " After making your change, you will need to re-import advection data, because new stations may 'come into" " view'. If the change was large, you may want to experiment a bit more with the setting (and import data" " yet again). You can even change the wind direction (horizontal scroll bar) as part of this process." " " " There is also an automated option for this procedure: pressing the 'Search' button causes WXSIM to make" " several attempts to find an optimum fit to the imported wind directions, by adjusting the scroll bar to" " maximize the above described %, and re-importing data for the resulting new set of stations. In addition" " to trying to maximize the % fit, some consideration is also given to the number of sites found (more is" " better). If you want to optimize further, you can still change the home station wind direction and search" " again. In any case, your oversight of this process, and perhaps viewing of wind streamlines from another" " source, are useful. This automated option is fairly dependable, but may be slower than a manual fit." " " " NOTE: Many times the flow is sufficiently linear so that none of the above is called for. Most of the rest" " of the time, the curvature is gentle and a couple of manual clicks plus one re-import of data is all that's" " needed. If the fit is poor (best percentage less than, say, 25 - or even negative), this indicates a weak," " chaotic, or rapidly changing flow, and the Neutral advection option would be appropriate." * 95 900 3400 2700 5060 2580 2230 " Because of local topography, ground cover, etc., NGM" " and NAM FOUS winds (already adjusted by WXSIM from" " 'boundary layer' to 10 meters above ground level) and" " READY meteogram '10 meter' winds may differ from those" " measured at a given site, even with a properly placed" " anemometer. The 'Wind factors' allow further custom-" " ization to the site. The default values (100% for many" " sites) are part of the customization, but you can change" " them at runtime and your modifications will stay in effect" " until you change sites, exit the program, or change them" " again. Basically, the values are percentages of the" " model winds. NOTE: these values affect only data being" " imported; changing them after import will have no effect." * 96 3340 2620 2450 4960 1800 2140 " The value entered here is the number of degrees the" " planned wind direction must stray from the original" " (or latest) value in order to elicit an actual change in" " the program, along with a prompt for new advection" " data (and termination of the previous advection profile)." " " " The default value of 40 is usually appropriate, but if" " larger changes are expected, which do not significantly" " alter the advection profile, a larger value may be OK." * 97 3340 2620 2450 4960 1800 2140 " If this box is checked, entered precipitation will fall" " intermittently, with three times the entered intensity," " during about the middle third of the entered time. This" " is very useful if the precipitation is expected to be" " showery in nature, and is especially important in such" " cases because sunshine could occur between showers" " and significantly raise temperatures above what they" " would be if the precipitation were continuous. If steady," " uninterrupted precipitation is expected, uncheck it." * 98 3340 2040 2600 4720 1220 2020 " This box is enabled when 850 mb (700 mb for sites" " above 2500 feet) relative humidity was imported from" " the READY site. If checked, it gives the program" " permission to use the data to alter the dew point in" " level two. This can have a small effect on surface" " temperature and dew point, as well as on the auto" " cumulus routine." * 99 3400 3620 3320 5250 2770 2280 " This box is enabled when 850 mb (700 mb for sites above" " 2500 feet), or Level 1 (usually about 925 mb), temperature" " data has been entered. If checked, it gives the program" " permission to (slightly) increase these temperatures if" " the lapse rate in the lower atmosphere exceeds the dry" " adiabatic rate (about 10 degrees C per km or 5.5 degrees" " F per 1000 ft). This occurs if surface heating is strong" " enough to convect heat up to that level. It amounts to a" " sort of compromise since cold 850 mb temperatures already" " tend to lower the surface temperature. The main effect of" " checking the box will be to slightly increase daytime" " temperatures above what they would otherwise be in cases" " of cold air advecting in at 850 mb. Basically, it allows" " WXSIM's native routines to have more influence." * 100 3200 5160 8800 5090 4320 2220 " Default or latest values are shown for the distance to the" " water and its direction from you, along with its surface" " temperature. Note that this temperature is corrected for" " your altitude above the water; if you are entering your" " own value, subtract a degree F for every 200 feet, or a" " degree C for every 110 meters you are above the water." " To help with this, the 'effective for sea level' box shows" " what the actual sea surface temperature would be with" " your entered value." " " " If you change the date or location, the routine will be" " disabled because water temperature would presumeably" " change. You can then reactivate it to establish the new" " water temperature." " " " Note that you have a choice of using default (climato-" " logical) sea temperatures or entering your own. The" " default values are usually sufficiently accurate and are" " updated for each day of the forecast. If you choose to" " enter your own values, be sure to do so frequently (at" " least once a week) as your entry will be used until you" " you change it, and could soon become quite inaccurate." * 101 3740 2290 3660 5010 1460 2220 " Default or latest values are shown for the direction" " uphill and the magnitude of the mountain/valley breeze" " effect, expressed as the amplitude (departure from no" " effect) of the wind speed component along the slope, in" " knots, on a typical clear day with otherwise light winds." " This is only an approximate way to quantify the effect," " so the wind speed variations you get may be somewhat" " different." * 102 2600 1720 3000 4700 920 2060 " Vapor pressure is the partial pressure of water vapor" " in the air, measured in millibars (hectopascals). It" " provides a very direct measure of humidity, since it" " is directly proportional to the actual amount of water" " vapor present." * 103 2600 1720 3000 5400 920 2420 " Mixing ratio is the ratio of the mass of water vapor in the" " air to the (much greater) mass of dry air. It is reported here" " in grams per kilogram and provides a very direct measure of" " humidity, since it is directly proportional to the actual amount" " of water vapor present." * 104 2800 1840 3120 5040 1020 2240 " This option generates best-fit (least-squares regression)" " straight lines for the upwind temperature and dew point" " profiles. In most cases, the Smooth Curve or Multi-Curve" " options will produce a better fit, but if you have reason" " to believe the upwind gradients to be linear, the present" " option may be best." * 105 1600 1840 2750 5800 1020 2620 " 'Distance Ratio' is the ratio of the distances to sequential upwind" " sites for which data is found, less than which the program will" " simply combine the two sites into one by averaging the positions" " and data. It is best left near the default of 1.15, but values as" " great as 1.3 or as small as 1 (for which no combining of sites will" " occur) are allowed." * 106 1280 3800 680 5200 2980 2320 " The freezing level given here is the highest level above" " which no temperatures are above freezing. In other words," " it is a 'top down' approach, so that the first above freezing" " temperature found starting from the highest level (300 mb)" " is taken as the freezing level. If the entire sounding is" " below freezing, the surface is given. The level is found by" " linear interpolation, with respect to height (not pressure)," " between WXSIM's 5 levels plus surface and top of the" " boundary layer. Note that the value may change abruptly" " if the top of an inversion layer suddenly crosses the" " freezing mark. Also, note that the units here can be" " toggled between feet and meters, and that the freezing" " level in the output text (menu option 8) will be in feet if" " you are using Fahrenheit and meters if you are using" " Celsius. You may toggle this during the run with interrupt" " code 'u'." * 107 5200 1700 3580 5460 880 2420 " This is the total sky cover in percent, accounting for overlap" " of clouds in multiple layers. For example, 50% coverage in" " level 2 combined with 60% coverage in level 5 would yield a" " total sky cover of 80%. The thickness (opacity) of the clouds" " is not considered here." * 108 5200 1900 4500 5120 1080 2260 " This is the intensity (in Watts per square meter) of global" " (direct and diffuse) visible solar radiation. It takes into" " account clouds, haze, fog, precipitation, sun angle, and" " distance from sun. On partly cloudy days, it should be" " considered an average, as minute-to-minute changes may" " be large." * 109 5200 2100 4800 5120 1280 2260 " This is the standard ultraviolet index, representing global" " (direct and diffuse) UVB solar radiation. It takes into" " account clouds, haze, fog, precipitation, sun angle, and" " distance from sun, and each unit corresponds to about 25" " mW per square meter. On partly cloudy days, it should be" " considered an average, as minute-to-minute changes may" " be large." * 110 1600 6540 5000 5600 5700 2500 " Here you can enter the current amount of ozone over your" " area in Dobson units. It is usually between 200 and 400, with" " 300 being a good world-wide, year-round average. The actual" " amount for the day, as well as forecast values for coming days" " can be found - usually in map form - on various web sites," " such as Environment Canada's:" " " " http://woudc.ec.gc.ca/e/ozone/Curr_allmap_g.htm" " " " or that of TEMIS/ESA (which has a text option):" " " " http://www.temis.nl/uvradiation/nrt/uvindex.php" " " " If you want WXSIM to use forecast values for upcoming days," " you can construct a simple text file with the first three lines" " being the numbers of the month, day, and year, and successive" " lines being Dobson unit values for each day, starting with the" " first day of the forecast. The file should be saved into the" " same folder as WXSIM, with the name being 'dobunits' followed" " by the first three letters of your site name. The data will be" " used only if the date and location in the file match the actual" " date and location. See the example dobunitsAtl.txt, for Atlanta" " on December 31, 2007, included with WXSIM's installation." " " " If you use data from sites such as above in a WXSIM forecast" " which you then publish, you should credit the source of the" " data, even though it is used only indirectly by WXSIM. Some" " sites have specific instructions regarding what copyright" " information you should display." * 111 20 8420 400 6460 7620 2910 " These are combinations of various stability indices, with some diurnal" " adjustments, for estimating of the likelihood of thundershowers, or of" " severe thunderstorms. After reading many descriptions of the meaning of" " different values of the various indices, I combined them, with weights" " according to their utility with regard to showers or severe thunder-" " storms. Perhaps the best way to define them is to point out that, first," " negative values mean convective activity is very unlikely. To see what" " positive values mean, study the following table, where the first number" " is the thunder/showers index, and the second is for severe weather." " " " 0 0 No shower or thunderstorm activity expected" " 1 0 Showers very unlikely" " 2 2 Showers unlikely" " 2 2 Showers unlikely, but could contain lightning if they occur" " 2 4 Isolated heavy thunderstorms possible" " 2 6 Isolated severe thunderstorms possible" " 3 1 Scattered showers possible, but thunder unlikely" " 3 3 Scattered showers and thundershowers possible" " 3 5 Scattered showers and thundershowers, some may be severe" " 4 1 Scattered showers likely, but thunder unlikely" " 4 3 Scattered showers likely, with some thundershowers" " 4 4 Scattered thunderstorms likely, some heavy or possibly severe" " 4 5 Scattered thunderstorms likely, some severe" " 5 1 Numerous showers likely, but few with thunder" " 5 3 Numerous thundershowers likely, some possibly heavy" " 5 4 Numerous thunderstorms likely, some severe" " 5 6 Numerous thunderstorms likely, many severe" " " " Note that separate calculations are available for North American and" " Northwest European climates, as different indices have been found more" " useful in different regions. I am not sure which version would be best" " for any particular other regions. Also note that these convective outlook" " indices vary diurnally more than do the individual indices themselves, so" " should be interpreted more as likelihoods of convection in the next few" " hours, rather than a morning value predicting afternoon conditions. This" " is appropriate for a forecast index, as opposed to one based only on a" " morning sounding and used to predict activity later in the day. Finally," " notice that once rain starts, the outlook may change rapidly as the local" " atmosphere stabilizes, making convection less 'likely' once it has started!" * 112 4800 2240 3600 6020 1420 2740 " These 'stability indices' provide some indication of the chance of" " convection, such as showers, thundershowers, severe thunder-" " storms, and (to some extent) tornados. The Boyden and KO indices" " are mainly used in Northwestern Europe, with the others widely used" " in North America (perhaps mainly the eastern two-thirds). All are" " probably useful in most places. For definitions and meanings of" " each, click on their respective blue-text captions." * 113 5000 3240 2800 6060 2420 2760 " Here you can specify the timing, duration, and magnitude of various" " types of solar eclipses. Enter the day number of the forecast (i.e." " 2 for an eclipse on the second day of the run) and select the type of" " eclipse. First and last contact refer to the times (same formats as" " on Entry form) when the moon first and last 'touches' the solar disc." " For partial eclipses, enter the 'magnitude' of the eclipse, as the" " maximum percentage of the sun's *diameter* (not area) to be covered." " In this case the moon's disc is assumed to have the same angular" " diameter as the sun's. For total or annular (a 'ring' of sun showing)" " eclipse, specify the duration of totality or annularity in minutes." " In any case, the maximum areal coverage is shown in the box below." " You can enable/disable the eclipse using the check box." * 114 4890 3530 2600 6090 2740 2760 " Here you can specify which data - gathered from a local (i.e. home)" " weather station by WXSIMATE - you wish to use in the forecast" " run. The data can be used in three ways. First, current data for" " many variables can be directly used to fill out the Data Entry form" " (along with current precipitation if it is occurring). Second, recent" " temperature and precipitation data can be used in the corresponding" " 'refinements' section. Finally, clouds, wind, estimated haze, and" " precipitation can be used to control the calibration run, generally" " allowing a more accurate initialization of WXSIM." " " " WXSIMATE, a companion program to WXSIM, provides automated" " download of most types of internet data used by WXSIM, as well as" " the local station data discussed above. It is available separately;" " for more information, see http://www.wxsim.com." * 115 4100 4200 2820 5820 3380 2580 " For many locations, most warm season rain falls in the form of" " afternoon and evening thundershowers, which happen only after" " sufficient solar heating has occured, often near the time the daily" " high temperature would occur even in the absence of showers." " The model data that WXSIM can import (FOUS and/or READY)" " usually reflect this diurnal pattern, but their 3, 6, or 12 hour time" " resolution often causes WXSIM to start the rain too early, leading" " to significant under-forecasting of the afternoon high." " " " A partial solution to this problem is the shower option for FOUS" " or READY data, but even then the showers often occur too soon." " The 'Stop AM Rain' option allows the user to specify the earliest" " and latest times at which rain will be allowed, either as showers" " or steady rain. Default times are provided, but you can change" " them using the scroll bars on the Prevent AM Rain form. You can" " also toggle this feature off and on with interrupt code 'P'. If" " you turn it on for the first time during a run, the default times" " will be used." * 116 3160 5140 2180 7640 4320 3490 " Importing or specifying level 1 temperature is usually not necessary, since one of" " WXSIM's strengths is its modelling of surface and near surface temperatures. There are" " some occasions when it may be helpful, however, such as when a strong temperature" " inversion exists between levels 1 and 2. An example of this occurs in some areas in" " winter, when a strong flow of low level cold air is undercutting a warmer airstream" " just above it. Such a situation often exists when freezing rain or sleet occur." " " " You should take note of the level 1 pressure in the grid on the upper air form in" " order to decide just what pressure level(s) to import here. The GFS and NAM models" " (on the READY site) provide '3-D' temperature at levels in 25 mb increments (i.e. 950," " 925, etc.) in the lower levels. You should pick the one closest to WXSIM's level 1" " pressure, or even pick two, straddling it (WXSIM will average the two). If the cold" " air is very shallow, you may pick a level a bit closer to the surface." " " " Imported READY temperatures will adjust for small discrepancies between WXSIM's" " actual level 1 pressure and the one(s) you imported. If you click the data in yourself," " it assumes those values are already for level 1. You can have WXSIM ignore the data," " partially consider it, or lock to it by choosing 0, 50, or 100%, for 'L1T use:'." " " " NOTE: If your site is above about 3000 feet (900 m), WXSIM may think that the 850 mb" " temperature in the default READY suite is supposed to be a level 1 temperature. If this" " is not intentional, use Clear Selected to delete the orange curve, or choose 0%." * 117 3580 4360 3340 5420 3540 2430 " This feature allows you to either increase ('+' button) or" " decrease ('-' button) the values of all imported or clicked-in" " values of the selected (via option buttons, above) data type." " In other words, you can raise or lower an entire curve of the" " graph. You can also click directly on the graph if you have" " reason to alter certain sections of a curve, but the 'Adjust'" " method is much quicker if you suspect an overall bias in the" " data type throughout the forecast period. The number in the" " text box at right shows the net adjustment so far to that" " particular item. Returning this number to zero restores the" " original values." " " " One reason for using this feature is if, after experience with" " READY data in your area, you have noticed a bias in the" " external model (i.e. GFS) data. For example, if GFS consis-" " tently makes it too cloudy, you can quickly adjust the clouds" " 'to taste'. You may simply want to use it for experimentation" " or testing different scenarios." * 118 2800 3400 3120 5880 2580 2600 " This generates more complex curves for the upwind temperature" " and dew point gradients than does 'Smooth Curve'. The curve is" " a linear combination 'Smooth Curve' solutions for the closest and" " farthest halves of the advection data. It is smooth (except for a" " slight discontinuity in slope near the end of the data) and may" " contain an 'inflection point'. This often allows a better fit than" " 'Smooth Curve'; you can look at the appearance and root mean" " square errors on the gradient plot to decide whether or not it is" " called for. As with 'Smooth Curve', you can use the 'Mono' scroll" " bar to slightly modify the shape (often not for the better). In most" " situations, 'Multi-Curve', with 'Mono' on a low setting may be the" " best choice. Remember that very suspicious stations can be" " removed from the data using the 'Ignore' button." * 119 3100 3600 3290 5500 2780 2430 " This option allows certain aspects of the advection routine to" " ignore sites beyond the distance you set using the scroll bar." " In particular, any of the smoothing options (that is, everything" " except straight line fit) will leave these distant sites out of the" " fit. The wind speed and percent fit to flow items (above the" " 'Search' button) will omit them as well." " " " The purpose if this is to allow flexibility when air may in fact" " never arrive from the distant sites, at least not during the" " forecast period or before a wind shift. However, the distance" " should be long enough to get plenty of sites for a reliable fit." " Commonly used values might be between 400 and 800 miles." " Note that the next value past 1499 miles is 3000, assuring" " that no sites will be missed for any customization." * 120 4360 3850 6000 4480 3000 1990 " If the 'Archive' box is checked, additional copies" " of the forecast data ('latest.txt, .wxf, and .csv)" " will be saved, but with names in the format 'f'," " followed by the date and time as yrmodahr, with" " the hour rounded to the nearest whole hour, local" " time. Files of the same name will be overwritten." " Any of the three buttons below will trigger this" " action. Note you can use 'Save Forecast' to save" " the data with your choice of name. If you check" " '.wxf only', then just the .wxf files will be saved," " to save disk space. Note that you can specify a" " directory for archived files by clicking the 'Save" " Forecast' button above, browsing to and selecting" " the folder, and then saving a forecast. WXSIM" " will remember your choice." " " * 121 2800 5540 4040 7860 4730 3600 " Careful, 'manual' use of WXSIM is strongly recommended, as it usually produces better" " forecasts and is certainly more instructive. However, you have the option here of pro-" " ducing automated runs, either on command (the 'Run immediately' check box) or pre-" " scheduled, as often as hourly if you wish, starting a specified number of minutes past the" " hour. Many choices you normally make when running the program can be predetermined" " here, and others made as usual on the Data Entry form. When prescheduling runs, you" " have the option of leaving the forecast on the screen until about a minute before the" " next, or having it revert to the Data Entry form (which you can miminize after choosing" " your settings. You can also set WXSIMATE to automatically gather data for these runs," " preferably about 10 minutes past the hour and about 5 minutes before the scheduled" " WXSIM runs. Forecasts are saved automatically and can be archived if you checked" " that box on the Output form previously. There is a slight chance during auto runs of some" " error or problem occurring that might stall the program without you there to handle it. One" " solution is to use System Scheduler to open and close WXSIM just before and after its" " scheduled runs. See the manual for details." "" " Choices for smoothing routines are simplified somewhat here, compared to manual mode," " but there are some options. By default, initial advection data is fit using smooth/" " 50% monotone, except that 100% monotone is applied if there is a significant temperature" " inversion. You can 'enforce monotone', (100%). This is useful mainly for preventing" " occasional unrealistic fits, mainly near coastlines or other places with sparse data." " MOS and GFS advection uses these same default fits. If MOS and GFS data are absent" " or depleted, either 'neutral' or 'default frontal codes' is used, according to your choice." " Frontal codes will use the default value and a 'straight line (segment) fit'." * 122 540 6880 5000 6820 6080 3100 " This routine allows you to compare previously made forecasts (via the .wxf" " files) with data from your own weather station, if you use Brian Hamilton's" " Weather Display, Davis WeatherLink, or Ambient's Virtual Weather Station," " and WXSIMATE. For Weather Display, you must specify the directory where" " your log files (...lg.txt and also ...vantagelog.txt, if you have it) are located." " If you normally access your data over the internet, you can set WXSIMATE to" " download the files from that site (in its normal fetching of WD data), in which" " case the directory is the 'current' one (i.e. c:\wxsim). To use WeatherLink or" " VWS data, you must have imported local station data using WXSIMATE," " which will have automatically saved text files of the needed data, for the" " specified and previous months, into the current directory." " " " The forecast must be one you've already run at least a few hours ago, or -" " better yet - a few days ago, so that a few days of data can be compared." " Averaging and interpolating is done on both data sets to produce half-" " hourly values, which are graphed and analyzed to get average absolute and" " net errors for 6-hour periods, whole days, and the whole forecast period" " for which both data sets are available. An average diurnal range (12-6 PM" " minus 12-6 AM) is calculated. You can select different variables to plot" " using the option buttons at left." " " " An extremely useful feature is the ability to combine results of many forecasts" " to more reliably show any trends or biases. To do this, click the 'Combine" " data' box, click Close, then pick a different forecast (usually from a different" " day). When you 'Compare to Actuals' again, the results will be averaged." " If you check the box again and go through the same procedure, you will get" " an average of all three forecasts (weighted equally), and so on. A dozen or" " more forecasts should be combined to give truly usefull results. Thicker than" " usual plot lines indicate that results have been combined. Click 'List' to see" " which forecasts you've used so far, and 'Save as .csv' to generate a file" " (name of the first forecast with 'cd' inserted before .wxf) which you can view" " in a spreadsheet such as Excel." * 123 5360 3050 6100 4400 2200 1950 " If the 'Graphic' box is checked, the retrieval" " module (wret.exe) will be briefly activated and," " if you have previously checked 'Save Bitmap' on" " the Plots page in that program, a graphic called" " latest.bmp will automatically be generated, with" " the items you most recently specified. Note: On" " rare occasions some condition in Windows can" " cause errors with VB's Shell command, which is" " used if this box is checked. If so, try checking" " the 'ext boot' box and start wret.exe manually or" " using a program such as System Scheduler." * 124 4900 2850 6800 4480 2000 1990 " If this box is checked, a copy of the plots will" " be saved as a bitmap called latest.bmp. If, on" " WXSIM's output form, you checked the Graphic" " box this (retrieval) program will briefly be acti-" " vated and, if Save Bitmap was last checked here," " the bitmap will be produced automatically. This" " can be used to automatically generate graphs" " to upload to web sites when using WXSIM's Auto" " Run mode. These plots will be saved into the" " directory specified on the main page of this" " retrieval module." * 125 900 6700 6880 4780 5900 2140 " This form allows you to compensate for possible bias" " in READY data or in GFS data from Chris McMahon's" " GRIB parsing system. Data from 2007 had suggested" " a cold bias - especially around WXSIM's levels 1 and" " 2 - and a tendency to overforecast cloud cover and" " small amounts of precipitation. A new review of data," " however, from 2010 and early 2011, using NCEP's" " verification page at" "" " http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/" "" " suggests the temperature bias is almost gone. Also," " WXSIM forecast verification data in Atlanta for the" " same period shows almost no bias for clouds or pre-" " cipitation, either, so a new set of default bias settings" " was instituted in version 12.8.7." "" " If you have the professional version, you can change" " these settings if you have reason to. The sliders are" " a bit complex, and best illustrated by observing the" " effects on the sample raw values shown, by moving" " the sliders. The effects on actual model cloud" " amounts may be more subtle in actual forecasts due" " to overlapping of layers. The lower range of the" " precipitation intensity (less than 100) has the additi-" " onal effect of totally erasing precipitation rates of as" " much as 0.05 inches (about 1.2 mm) per day (that for" " the lowest setting, 50). Cloud and precipitation set-" " tings may vary, especially near mountains, where time" " and experience are needed to find the best settings." * 126 3340 2820 2450 5100 2000 2200 " The value entered here is the number of hours that can" " pass after an advection prompt (due to a planner-based" " wind shift exceeding the direction tolerance, or due to" " the item described here) before another advection prompt" " is triggered. This requires at least some wind shift." " " " A value of about 36 is usually appropriate, but a shorter" " period may be appropriate for North American sites using" " MOS, especially if a cold front with little or no wind shift" " is expected to pass during the forecast period." * 127 3540 4200 6600 4600 3370 2100 " If this box is checked, copies of soundings will" " be saved as bitmaps called soundingx.bmp, where" " x is the sequential number of the data point. If" " on WXSIM's output form, you checked the Graphic" " box this (retrieval) program will briefly be acti-" " vated and, if Save Bitmap was last checked here," " along with Inc Soundings, these bitmaps will be" " produced automatically. This can be used to" " automatically generate graphs to upload to web" " sites when using WXSIM's Auto Run mode. These" " plots will be saved into the directory specified" " on the main page of this retrieval module." " " " The 'Every (n)th' value(n) determines which of the" " large number of potential soundings gets saved. In" " many cases, there are 2 data points per hour, so a" " 12 in the box means there will be 6 hours between" " saved plots." * 128 30 10780 5680 6240 9960 4220 " This feature allows you to automatically compare a large number of" " forecasts to actual data. First, select the first (in terms of date)" " forecast in the group you want analyzed. Then, click 'Compare" " to Actuals to view the forecast compared to actual data. This gives" " you a chance to check settings and it also prepares the Auto Select" " routine. Next, click 'Set as Earliest Date'. Finally, select the last" " forecast in the group you want analyzed, and click Auto Select." " " " You should now see all .wxf files in the directory being selected to" " determine which ones fall between the selected dates, are for the" " same site, and are not marked by WXSIM as lacking in appropriate" " data. After this, the Auto Compare form appears, with scrolling text" " showing the results of forecasts out to three days *past* the date of" " the forecast. A variety of data appears at the end (though it's" " possible that scrambling may happen with large data sets - scroll" " until you find the summary information." " " " You can view two types of graphs of the data, but the main purpose" " of this feature is to allow construction of a small file that WXSIM (in" " professional mode) can use to fine tune its forecasts. If you use this" " feature perhaps once or twice a week, and with months of data," " WXSIM's forecasts (again, if you have professional mode) of tem-" " perature and dew point should gradually become more accurate." " " " You can omit specific forecasts from the run by selecting them, one" " at a time, and pressing 'Omit'. Another feature is that you can view" " the regular comparison plots for a large group of forecasts. Select" " the first forecast of the group you want, click 'Compare to Actuals'," " and check 'Combine data'. Click 'Close' and select the *second*" " forecast as the earliest. Select the *second-to-last* forecast and" " click 'Auto Select'. After the analysis (which averages data differently" " in this case, so do *not* approve this as your correction data) is" " complete, select the last forecast of the group and click 'Compare to" " Actuals'. Uncheck the 'Combine data' box before proceeding with any" " subsequent analysis." " " " If recent cloud cover and precipitation has been well predicted, it may" " be appropriate to check the 'Weight recent more' box. Otherwise, this" " box should probably be left unchecked." " " " Some users may not consider their own station data as the standard." " For example, I use data from my school's weather station, but want" " the forecasts to be for Hartsfield-Jackson Airport (KATL). Comparing" " several months of the school station's data to that from KATL showed" " KATL averaged 0.32 F cooler, with a diurnal range 1.08 times greater," " than the school's. So, I entered -0.18 (Celsius, = -0.32 F) in the Dep" " box and 1.08 in the Rng box." " " " To use this data in WXSIM, click on the 'READY/GFS Bias Factors'" " button in WXSIM (on the Data Import form), and check the appropriate" " box on the form that appears. Also, click on 'Start Autolearn' for" " information about automating the entire process." * 129 2250 6530 5320 4650 5700 2080 " If this box is checked, WXSIM will use bias" " correction factors (displayed below) from the file" " 'cor.txt', which can be created using the retrieval" " module (wret.exe, accessible via File/Retrieve)." " If you have a home weather station which logs data" " readable by WXSIMATE and you have archived" " forecasts at least four days in length, for at least" " the last five days (preferably several months), you" " can use the 'Auto Select' feature in wret.exe, or" " the program autolearn.exe, to create cor.txt." "" " If you use the feature here, any saved forecast" " will contain information on the correction factors" " used, so that the values can be steadily improved" " over time by repeating the process." " " " Some users may not consider their own station data" " as the standard. For example, I use data from my" " school's weather station, but want the forecasts to" " be for Hartsfield-Jackson Airport (KATL). Comparing" " several months of the school station's data to that" " from KATL showed KATL averaged 0.32 F cooler," " with a diurnal range 1.08 times greater, than the" " school's. So, I entered -0.18 (Celsius, = -0.32 F)" " in the Offset box and 1.08 in the Range factor box." " If you regard your weather station as 'official' for" " forecast purposes, keep 0 and 1 in the 'Dep' and" " 'Rng' boxes in wret.exe. The values shown on the" " current form are just copies of those in wret.exe." * 130 2500 3020 5120 5730 2200 2560 " If this box is checked, and a nocturnal temperature inversion" " of a threshhold strength forms, WXSIM will reduce (moreso with" " stronger inversions) maritime moderating influences and also" " the strength of any warm air advection that might be occurring." " " " The main purpose and effect of this feature is to lower nighttime" " temperatures on clear, fairly calm nights in coastal and near" " coastal regions, where some WXSIM users had reported too-high" " forecast lows under these conditions. Actually, most of these" " reports came from New Zealand, and only in winter, so use in" " other places at other times may be questionable." * 131 2800 5060 4620 5950 4240 2670 " This form allows specification of a large number of soil-related" " variables, and optional activation of routines which allow WXSIM" " to model soil temperature, moisture, evaporation, and other items" " of mainly agricultural interest. Most of the data on this page can" " be set by the user and will be stored in memory and saved to file" " for later use. Temperature and moisture values initialize on this" " form with default values estimated from atmospheric and other data," " unless you have just imported soil temperature and moisture data" " from a home weather station using WXSIMATE, in which case the" " values are interpolated/extrapolated from that data (assuming the" " date and hour match WXSIM's initialization time). The name of the" " file containing imported soil data is soildata.txt. You can also" " change data manually on this form." "" " If you wish to see the effect of planned irrigation, you can enter" " irrigation data (using the same units you would for rainfall) on the" " Interrupt Planner right before the start of a forecast, by clicking" " intensity values directly on the graph." "" " To see soil data in WXSIM's output, choose up to five items from" " the bottom of this form and also choose item 10 under Output Menu" " on WXSIM's Data Entry form." * 132 5000 2270 4620 5330 1450 2360 " Albedo is the fraction of visible light reflected by a surface." " Examples of approximate values:" " " " asphalt 0.04 to 0.12 dark, wet soil 0.10" " conifer forest 0.10 broadleaf forest 0.16" " bare, dry soil 0.17 to 0.28 grass and most crops 0.20" " wet/dry sand 0.25/0.40 old/fresh snow 0.45/0.85" * 133 5000 1870 4620 5630 1050 2510 " Leaf Area Index (LAI)is the ratio of total upper leaf surface area" " of vegetation divided by the surface area of the land on which" " it grows. It ranges from 0 for bare ground to 6 for dense forest." " For crops, LAI may be only 1 or 2 early in the growing season" " and increase to perhaps 4 by harvest time." * 134 5000 2670 4620 5690 1850 2540 " The light extinction coefficient allows estimation of the fraction" " of incident light transmitted by a plant canopy, as a function of" " leaf area index (LAI), according to" " " " transmitted intensity = incident intensity * exp(-k * LAI)" " " " where k is this light extinction coefficient. It ranges from about" " 0.4 for vertically distributed leaves to about 0.7 for random leaf" " orientations, and theoretically as high as 1 for horizontal leaves." * 135 5000 1870 4620 5630 1050 2510 " Various kinds of mulch or ground cover, such as pine straw or" " wood chips, contribute an insulating effect in addition to any" " plant cover effects. The scale used here refers to inches of" " loosely packed pine straw or wood chips, based on experiments" " done WXSIM's author. Note: 1 inch = 2.54 centimeters." * 136 5000 1670 4620 5730 850 2560 " This is simply the height of the top of the growing vegetation" " above the ground. WXSIM uses this information in calculating" " evapotranspiration. Heights above 30 centimeters (about 1 foot)" " make little additional difference in WXSIM." * 137 5000 1670 4620 5730 850 2560 " Runoff tendency is a relative term in WXSIM, ranging from 0 (no" " runoff beyond that due to soil moisture) to 1 (no precipitation" " enters the soil). This is not a very well defined parameter, so" " users may want to adjust it based on experience over time." * 138 5000 1670 4620 5730 850 2560 " The custom diffusivity factor allows users to adjust soil thermal" " diffusivity (even with fixed soil type) according to experience" " gained over time. If you see greater temperature variations at a" " given depth than WXSIM forecasts, you can increase the value." * 139 5000 1670 4620 6330 850 2860 " WXSIM's soil temperature and moisture algorithms are very calculation" " intensive, usually at least tripling the time needed for a run to complete." " If you do not need the soil data forecast, you can uncheck this box to" " allow WXSIM to run at full speed." * 140 4450 2670 6120 6210 1850 2800 " Thermal diffusivity is the soil's thermal conductivity divided by its" " volumetric heat capacity. It is a measure of how well temperature" " changes at the soil surface penetrate to greater depths. The depth at" " which temperature variations are reduced to half that at the surface is" " proportional to the square root of the diffusivity and also the square" " root of the time period of the surface temperature variation. For" " example, a diffusivity of 0.0045 cm^2/sec cuts the amplitude of daily" " temperature variations in half at a depth of 7.7 cm (3 inches) and cuts" " that of annual temperature variations in half at 1.47 meters (almost" " 5 feet)." * 141 4450 2270 6120 6010 1450 2700 " To set soil properties (which are saved on exit from WXSIM), select" " the layer you want to modify, corresponding to the depths at far left." " Then select the soil texture from the rather standard 'soil triangle'." " Finally, you can modify this by specifying an admixture of rock or" " organic (i.e. peat) components. 100% rock is just that - solid rock," " while 100% organic is pure peat. You can specifically set the" " properties of each of the five layers in this way." * 142 5000 1670 4620 6790 850 3090 " You can specify soil depth at which you want to enter and model temperature" " and moisture (note the inches or centimeters choice below). These depths," " temperatures, and moisture values are interpolated and extrapolated onto" " WXSIM's 30-layer model, and then mapped back onto your depths for output." * 143 5000 1670 4620 6490 850 2940 " This form is initialized with soil temperatures estimated from climatological" " data, current weather conditions, and (optionally) recent temperatures" " (entered in 'Refinements' on the Data Entry form). You can overwrite the" " estimated soil temperatures if you have your own soil thermometers." * 144 5000 1670 4620 6210 850 2800 " This form is initialized with soil moistures estimated from climatological" " data, current weather conditions, and (optionally) recent precipitation" " (entered in 'Refinements' on the Data Entry form). You can overwrite" " the estimated soil moistures if you have your own soil moisture probes." * 145 6500 1270 5820 6050 450 2720 " Any five of the items below can be displayed in WXSIM's output. To" " view these, select item #10 under Output Menu on the Data form's" " Entry top menu bar." * 146 3000 4000 1920 6190 3180 2790 " 'Agricultural data' refers here to soil temperature and moisture at" " 5 depths defined by the user in the forecast, temperature at the top" " of short grass, at the top of the soil, and 15 meters (50 feet) above" " the ground - plus a variety of evapotranspiration and radiation data." " These items are forecast only if enabled in the professional mode of" " WXSIM, so the associated check boxes will be disabled for forecasts" " which did not include the data. The soil depths used are displayed" " in the lower-right part of the 'Other Data' frame." " " " Soil moisture is expressed in percent by volume, with soil moisture" " tension in centibars (kilopascals). Evapotranspiration rates are in" " inches per hour if Fahrenheit was selected and millimeters per hour" " when using Celsius. Total evapotranspiration is accumulated from the" " start of the forecast and is similarly expressed in inches or millimeters." " Irrigation (planned by the user on WXSIM's Interrupt Planner) rate and" " total use the same units as does precipitation." * 147 500 8700 200 7380 7850 3360 " Imported forecast data from the GFS and (for U.S. users) NAM models forms the" " basis for WXSIM's forecasts of clouds, precipitation, and wind (with temperature" " and humidity somewhat more native to WXSIM's own routines). There are various" " options, in the professional mode, for making global changes to such data using" " user-defined bias factors. However, some sites have strong local effects, such" " as orographic up- or down-slope flow, or 'lake effect' precipitation, which occur" " under specific conditions of wind or temperature, and which the GFS model, with" " somewhat low resolution, cannot quite 'see'." " " " To address these problems, WXSIM offers user-controlled tools for modifying GFS" " data, or any data entered on the Interrupt Planner form. These settings should" " be decided by the user, based on experience and understanding of local weather" " effects, but a very rough initial guess for these values can be set using the" " 'Assign Site-Specific Defaults' button." " " " All three of these routines have a 'strength' setting, from 0 to 100, which probably" " can be applied through all seasons once a good value has been determined. The" " wind direction settings refers to the direction from which the surface wind is blow-" " ing when it has the particular effect is at its greatest (changes in wind direction" " with height complicate things and are not considered here). Effects are strongest" " with winds from the exact direction, but have some effect up to 90 degrees from that" " direction. Effects also increase with wind speed, up to a bit more than 20 miles per" " hour (32 km/hr). Lake effect precipitation also strongly considers the lapse rate" " between the water surface (temperature can be either default or a value entered for" " the Diurnal Breeze routine, if it is in use). Convective enhancement of precipitation" " starts with lapse rates 1 degree C shy of the dry adiabatic rate between the surface" " and level 2 (i.e. a water minus 850 mb difference of 11 or 12 degrees C in the case" " of the Great Lakes) and 'maxes out' at a rate 7 degrees past dry adiabatic." " " " The maximum enhancement of precipitation from the upslope or lake effect routines" " is a factor of 5. The greatest diminishment of precipitation sing the downslope" " routine is to just under 20% of values from the Interrupt Planner. Cloud cover" " varies in the same direction as does precipitation, but in a somewhat less aggres-" " sive and complex way. All of the routines can be used together, and their effects" " are combined so they may produce greater extremes, or perhaps tend to cancel out." " The changes to GFS or other data on the Interrupt planner are in addition to any" " model bias factors you may have entered. Data from NAM FOUS is not altered." " " " These features should be used with careful consideration, and if no well-defined" " local differences from GFS data are known, are perhaps better left set to a strength" " of zero." * 148 300 7000 1360 10260 6150 4780 " You can optionally allow WXSIM to include descriptors for temperature and wind speed in the plain text output. If you" " would like this done, check the 'Allow descriptions button. You can control the thresholds for the various terms for" " both temperature and wind. Choose 'Weak' for relatively 'toned down' and less frequent descriptions. 'Medium' is the" " recommended setting, but you can choose 'Strong' if you want more impact in the wording. The wind options are" " rather straightforward, with thresholds for the three terms directly defineable. Note that these refer to average wind" " speeds over each of the 12 hour forecast periods (day and night)." " " " The temperature descriptions are rather sophisticated. There are four 'tiers' of terminology, triggered (for 'medium'" " strength) at 1, 2, 3, and 3.4 standard deviations from normal maximum or minimum temperatures (for day and night," " respectively. One standard deviation corresponds to occurrence of that temperature or something more extreme about" " once per week, while two standard deviations is something exceeded once every month or two, or once on that" " specific date every 44 years. Three SD's would likely exceed the all-time record for the date, and 3.4 would be near" " the all-time record for the month over the course of a century. Seeing extremes in a forecast is not as rare as it might" " seem, because in a 7 day forecast, there are 14 chances to do so (7 maxes and 7 mins), and they may be exceeded" " either on the high side or the low side. This means there is an almost even chance of a second tier description" " appearing, and first-tier ones may occur a few times in a typical one week forecast." " " " The temperatures (for the first 3 tiers) also consider wind chill - compared to wind chills with normal wind and" " temperature - as a 60/40 mix. Furthermore, they consider both relative values (compared to normal for the date and" " location) and absolute aspects, so that, for example, an 86 degree F (30 C) afternoon high in Phoenix, Arizona - while" " far below normal - would not be called 'cold'. The first 3 tiers also compromise between absolute and relative values" " with regard to day and night. For example, a below-normal night would more readily be called 'cold' than would be an" " equally below-normal day, because the night is in fact colder. However, departure from normal still accounts for 75%" " of the decision here." " " " The 4th tier has phrases starting with 'near record', like 'near record cold' or 'near record warmth'. These are" " triggered by depature from normal alone (no wind chill or absolute temperature consideration, except for things like" " 'low temperatures' instead of 'cold' when it's not really 'cold'). They are intended to refer to once-this-month in a" " century extremes, but may in fact differ considerably from this for a given site because of skewed ('non-Gaussian')" " temperature distributions. They will almost always correspond at least to extremes for the specific date over a" " century, however, while some sites may never have great enough extremes for them to appear." * 149 5000 4570 4620 5630 3750 2510 " Studies of WXSIM's modeling of soil temperatures suggest that" " ground cover such as turf grass provide insulation beyond" " that accounted for by leaf area index and light extinction" " coefficient. This may be due to trapping of air by blades of" " grass or thermal diffusivity differences due to the root system." " In any case, this parameter allows more realistic modeling." " " " Testing shows that a normal, reasonably full grass cover calls" " for a value here between about 1.5 and 2.0, to go along with a" " leaf area index of between 2 and 3 and a light extinction coef-" " ficient of about 0.5. For some reason, somewhat higher values" " near 2.5 seem to work best for modeling the response to cold" " air outbreaks in winter. A good compromise is about 2 for most" " of the year." " " " This item has about the same (perhaps a bit more) effect per" " unit change as the 'additional insulating effect' item below." " This 'base insulating effect' has a more direct effect on" " sensible heat transfer than does the other one, though." * 150 4000 5550 3020 5730 4730 2580 " WXSIM has always had the option, as a 'refinement' found on" " the lower right part of the Data Entry form, to enter initial snow" " depth and water equivalent. For some time there has also been" " the ability to maintain this setting between runs in auto run" " mode, simply by leaving the option 'on' (highlighted in red)." " " " This new 'Initialize with previously forecast snow cover' option" " allows WXSIM to consult a file created during the most recent" " forecast run, to find the forecast snow cover at the time of the" " new run. This depth results from any intial snow cover (either" " entered by you or by this routine from a yet earlier run), entered" " and accumulation, compacting, and melting that occurred during" " the forecast. Both depth and water equivalent are recorded and" " used. In manual mode, a message box will inform you of the" " amount (if greater than zero), though this message is suppressed" " in auto mode." " " " Message boxes will inform you if the data doesn't exist (which is" " to be expected the first time you use this) or if the date and time" " of the new forecast do not occur in the previous one. You can" " still enter data directly, to update and override the old data." " This new function can operate with the snow/ice refinement 'on'" " (red) or 'off' (blue). Most commonly, one might have it on," " supposing that there was snow to manually enter at some point." * 151 800 9050 3020 5990 8240 2640 " WXSIM calculates likely variations in wind speed, based on the" " predicted mean wind speed (for the specific output time) and" " atmospheric stability in the first layer (generally up to about" " 60 mb above the surface). The resulting brief (assumed" " sustained for about 3 seconds) maximum winds, or 'gusts' are" " calculated for two time periods - the highest in the surrounding" " 10 minutes (roughly the METAR and WMO standard) or the last hour" " (in METAR reports a similar figure is called 'peak wind'). You" " can choose which of these two standards you wish to appear in the" " plain text output. In either case, the figure is based on the time" " of highest mean wind of the 6 or 12 hour period." " " " You can also specify the lowest speed gust to be reported. In" " METAR reports, gusts are generally reported only if the lowest" " and highest winds differ by at least 10 knots. In practice, this" " means gusts are usually not reported if less than about 12 knots" " (14 mph, 22 kph, or 6 m/s)." " " " The Ratio Adjustment lets you alter your default gust factors," " which are multiplied by the mean wind speed to generate gust" " data, but you should do so only if you have strong evidence that" " the change is called for. The overall default value for this is 1," " but if you have an enhanced customization, you may have been" " given a different value." " " " You can see the effects on the gust factors by changing the ratio" " adjustment, the mean wind speed, or the surface minus level 1" " temperature difference. Higher gust ratios result from increasing" " the ratio adjustment or the temperature difference (as instability" " increase gustiness a bit), or by decreasing the wind speed (as" " fluctuations are a larger fraction of smaller mean wind speed" " values. The factors increase with the length of the time interval" " because longer times allow more chances for a high gust to occur." " " " The algorithms used here were developed by the author, using" " wind data from about 20 customers' log files, over 7600 gust" " reports culled from nearly 89,000 METAR reports, and consideration" " of two large studies (http://andvari.vedur.is/~haraldur/artikel.pdf" " and ams.confex.com/ams/pdfpapers/108357.pdf) done by others." " These data span the globe and the seasons. Local variations will" " occur and are accommodated by the ratio adjustment, but most" " sites should be fairly close to these worldwide means." * 152 1500 6150 6700 5990 5320 2640 " WXSIM calculates likely variations in wind speed, based on the" " predicted mean wind speed (for the specific output time) and" " atmospheric stability in the first layer (generally up to about 60 mb" " above the surface). The resulting brief (assumed sustained for" " about 3 seconds) maximum winds, or 'gusts' are calculated here for" " four time periods - the highest gust in the last 1 minute (as in" " Weather Display log files), the surrounding 10 minutes (roughly the" " METAR and WMO standard), the surrounding hour (in METAR" " reports a similar figure is called 'peak wind'), or the surrounding 6" " hours (the highest value of which during a day is very close to the" " maximum gust for the whole 24 hours)." " " " The Ratio Adjustment lets you alter your default gust factors," " which are multiplied by the mean wind speed to generate gust" " data, but you should do so only if you have strong evidence that" " the change is called for. The overall default value for this is 1." " The value here is saved independently from the similar quantity" " in WXSIM itself." " " " The algorithms used here were developed by the author, using" " wind data from about 20 customers' log files, over 7600 gust" " reports culled from nearly 89,000 METAR reports, and consideration" " of two large studies (http://andvari.vedur.is/~haraldur/artikel.pdf" " and ams.confex.com/ams/pdfpapers/108357.pdf) done by others." " These data span the globe and the seasons. Local variations will" " occur and are accommodated by the ratio adjustment, but most" " sites should be fairly close to these worldwide means." * 153 3400 4400 3000 5590 3570 2440 " Both in WXSIM and in reality, snow cover lowers temperatures," " largely by increasing the albedo (reflectivity) of the surface." " This effect is reduced considerably, however, if there are a lot" " of non-snow-covered objects (i.e. trees) protruding above the" " snow pack. Some of the most effective absorbers of sunlight" " are evergreen trees, such as pine, or especially fir and spruce." " WXSIM's site-specific customizations include a rough guess of" " the prevalence of such forests in the area, but users may well" " well want to adjust this, especially if experience with the" " program suggests problems with the effect of snow cover." " " " If you change the setting to a value significantly different from" " WXSIM's own very rough estimate, the descriptive text will" " appear in red as a cautionary message. It is perfectly OK to" " use a value that produced red text, as long as it accurately" " describes your surroundings. Note that nearby unfrozen bodies" " of water may warrant a 'forest' type setting, though this effect" " is reduced by the slowness of water to warm anyway." * 154 3400 3970 3000 5430 3140 2360 " WXSIM has carefully developed algorithms for estimating the" " likelihood of convective activity, ranging from showers to" " severe thunderstorms. These employ a variety of stability" " indices and there are options for either relatively warm or" " continental climates like North America, or cool, moist" " climates like Northwestern Europe. Seasonal differences are" " also taken into account, so this system should work fairly" " well regardless of season or location." " However, experience may show the forecasts to be either too" " aggressive or too conservative. This setting (which can be" " set independently in both WXSIM and the retrieval program," " wret.exe) allows the user a limited ability to customize the" " output by about one descriptive category in either direction." " A value of 0 is generally recommended, while +2 is the most" " aggressive setting and -2 the most conservative setting." * 155 2400 5370 4600 5930 4540 2580 " If this box is checked, the lastret.txt file (created when you" " 'View Text') will include, at the very end of each line of regular" " data, a code indicating the nature of any expected convective" " activity. The possible codes, along with their meanings, are:" "" " 0 No shower or thunderstorm activity expected" " 100 Showers very unlikely" " 201 Showers unlikely" " 202 Showers unlikely, but could contain lightning if they occur" " 204 Isolated heavy thunderstorms possible" " 206 Isolated severe thunderstorms possible" " 301 Scattered showers possible, but thunder unlikely" " 303 Scattered showers and thundershowers possible" " 305 Scattered showers and thundershowers, some may be severe" " 401 Scattered showers likely, but thunder unlikely" " 403 Scattered showers likely, with some thundershowers" " 404 Scattered thunderstorms likely, some heavy or possibly severe" " 405 Scattered thunderstorms likely, some severe" " 501 Numerous showers likely, but few with thunder" " 503 Numerous thundershowers likely, some possibly heavy" " 504 Numerous thunderstorms likely, some heavy or possibly severe" " 505 Numerous thunderstorms likely, some severe" " 506 Numerous thunderstorms likely, many severe" * 156 5700 2220 2860 6510 1400 2950 " When the sun is low in the sky, cloud cover and haze estimates derived" " by WXSIMATE from solar radiation data can be very uncertain, especially" " if hills, trees, or buildings block sun from the sensor. This setting enables" " you to specify a minimum sun altitude above the horizon (as of 30 minutes" " before the forecast start time) for which to allow WXSIM to apply the" " estimated cloud and haze data. This affects only the initial forecast data," " not the varying amounts during the calibration run." * 157 4000 4980 2860 6790 4160 3090 " Besides actual moisture content, another very important quantity, especially" " for crop irrigation decisions, is soil moisture tension. This is a type of" " negative pressure (measure here in centibars or kilopascals) representing" " the tendency of water to cling to soil particles. It also effectively measures" " the energy required for a plant to extract water from the soil via its root" " system. This number depends on both volume moisture percentage and soil" " type, in a rather complex way. Generally, values near zero correspond to" " saturated soil and higher values occur in drier soil. For a given moisture" " content, sandy soils will have smaller tensions than silty or clayey soils." " The mathematical function used here is an empirical fit to a large amount of" " data, but is not one of the 'official' versions (such as one by van Genuchten)." " It will usually have errors of less than about 5 percent moisture content for a" " given tension and soil type, however. WXSIM actually uses moisture content" " in its internal calculations, but returns tension values using an inverse" " function in such a way that given accurate initial tension values, forecast" " errors are only mildly affected by the less-than-perfect fit of this function." " " " Most plants thrive with values in the 10-30 centibar range. Irrigation may be" " appropriate with values over 30 cb in sandy soils and over 70 cb in clay." " Values over 200 are much to dry for most crops, though actual wilting may" " not occur values exceed 1000." * 158