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The Weather Prediction Center

Wingridds Macros (Scripts)
developed by the WPC International Desks

Since 2013, the WPC International Desks develop Wingridds macros/scripts to assess the potential for weather processes that affect the Americas. Access to a few of these, and installation instructions are available in the following table. Note that for the macros/scripts to work, you need to download the ALIAS.USR file and the color table files (available in the table). There are two options to download any file: (1) right click and download or (2) click, copy the text and save it with the file name.
Graphic description File download and Description
ALIAS.USR
Updated on 23-Mar-2018
COMMAND FILE (MUST DOWNLOAD)
Contains variables programmed by the user, and is required for the macros to work. Needs to be placed inside the "C:/WINGRIDDS/USER" directory. To download: (1) right click and download or (2) click, copy the text and save it with the file name.
GDIO.CMD
Updated on 23-Mar-2018
GDI, LOW-LEVEL MOISTURE CONVERGENCE, 3-D FLOW, MID-LEVEL VORTICITY AND UPPER DIVERGENCE
(HORIZONTAL ANALYSIS)

The macro provides a 3-D summary of the thermodynamical and dynamical processes relevant to the development of convection and rainfall in tropical and sub-tropical locations.
It plots GDI-type stability (shaded), which relates to the potential for different types of convection. Usually, greens/yellows and larger values suggest that the potential for thunderstorms exist. Oranges and reds often suggest that any convection that develops might have the potential of producing heavy rainfall. More on GDI interpretation can be found here .
The macro overlays low-level (1000-925-850 hPa) moisture convergence (green contours and boxes), which captures the low-level triggering of convection when moisture is available. This is important in features such as fronts, shear-lines, waves/troughs in the trades, and areas of orographically-induced convergence.
The low-level flow (1000-925-850 hPa) is overlaid using barbs [kt] and streamlines in black. Mid-upper flow (700-600-500-400 hPa) is plotted with white and yellow barbs [kt] and streamlines. Mid-level vorticity (red=positive and blue=negative) is used to infer the presence of mid troughs and ridges; and mid-upper divergence (600-500-400-300 hPa) are plotted with white and yellow solid and dashed contours). The latter relates to tropospheric ascent dynamically-induced by mid/upper features.
This macro needs to go inside your "C:/WINGRIDDS/MACROS/" folder. Note: Requires the ALIAS.USR and the color table CFCB.DAT , both placed in the folder "C:/WINGRIDDS/USER".
TWIN.CMD
Updated on 23-Mar-2018
TRADE WIND INVERSION
(HORIZONTAL ANALYSIS)

Macro/script designed to evaluate the height and strength of the trade wind inversion. This has implications in quantitative precipitation forecasting, as it helps to describe the depth of the moist layer and the vertical mixing with the overlying air.
It looks for the lowest potential inversion by calculating vertical temperature gradients in 50-hPa layers and plots it with a shaded color scale. Note that if many inversions are present, the macro/script will only consider the lowest one.
The strength of the inversion is depicted with black boxes (the larger the box, the stronger the inversion = the larger the temperature increase with height). No box means a gentle lapse rate, but no temperature inversion per say. Small boxes indicate increases of 0-2°C in the layer; large boxes mean strong inversions.
The macro/script also plots low-level (1000-925-850 hPa) moisture convergence (green contours and boxes); precipitable water > 36mm (light blue solid contours), relative humidity averaged over the 850-650 layer (orange or brown contours). The the mid-level flow [kt] is then overlaid with white and yellow barbs and streamlines.
This macro needs to go inside your "C:/WINGRIDDS/MACROS/" folder. Note: Requires the ALIAS.USR and the color table CFCK.DAT , both placed in the folder "C:/WINGRIDDS/USER".
GR01.CMD
Updated on 23-Mar-2018
HAIL POTENTIAL
(HORIZONTAL ANALYSIS)

Macro/script designed to evaluate the potential for hail in South America, but generally works well in subtropical latitudes in both hemispheres, particularly in the 25-40° latitude belt. The macro plots the 200-250 hPa winds in gray shades, to reflect the presence of upper jets and the potential enhancement of ascent by jet dynamics in association with jet maxima/streaks. Tropical-side entrances of jet maxima/streaks and polar exits both favor upper divergent and ascent.
The macro also plots wind barbs [kt] averaged over the 925-850 hPa layer in green, to evaluate low-level convergence, especially in associations with low-level jets. These are significant features in the triggering of severe convection in South America. Also, 1000-850 hPa moisture convergence (light blue contours).
High mixing ratios at 500 hPa relate to enhanced growth of hail stones in the level of supercooled water droplets. Thus, 500 hPa mixing ratios >0.8 g/kg are plotted with blue contours. Mixing ratios > 2 g/kg are ideal for hail growth. Some dry air in regions were temperatures are slightly above freezing favor evaporative cooling, a drop in temperatures, and preservation of hail stones that fall later. Thus, 700 hPa relative humidity in the 45-70% range is plotted (brown contours). Too much dry air (RH<40%) is often not good.
The boxes reflect the potential size of hail stones. These are based on the 700-500 hPa lapse rates, which reflect mid-level stability and relate to the strength of the updraft. Lapse rates>20°C/layer associate with violent updrafts (that help to maintain the hail stone longer on the growth layer) and large hail (large red boxes); while lapse rates of 16-20°C associate with small hail (small pink boxes).
This macro needs to go inside your "C:/WINGRIDDS/MACROS/" folder. Note: Requires the ALIAS.USR and the color table CFCX.DAT , both placed in the folder "C:/WINGRIDDS/USER".
TCB2.CMD
Updated on 27-Mar-2018
POTENTIAL FOR CONVECTION AND RAINFALL: INSTABILITY, WINDS, OMEGAS AND CB-TEMP
(VERTICAL CROSS/TIME SECTIONS)

Macro/script designed to evaluate the potential for convection and precipitation, especially in tropical and subtropical regions. Shows the vertical distribution of equivalent potential temperature (shaded color field and yellow contours). This is related to the heat and moisture content, and the potential for latent heat release. The larger the values in the column, and the deeper the column, the larger the potential for moist convection and the larger the potential rainfall amounts.
It also shows wind barbs [kt] in magenta; omegas (white arrows); mixing ratios (green dashed contours); and temperatures colder than -20°C in solid red contours. The latter is to assess the potential for electrification, as it becomes more likely once convection reaches -20°C since this tops the likelihood for the development of ice crystals (CB-TEMP=Cumulonimbus temperature).
This macro needs to go inside your "C:/WINGRIDDS/MACROS/" folder. Note: Requires the ALIAS.USR and the color table CFCT.DAT , both placed in the folder "C:/WINGRIDDS/USER".
DVRH.CMD
Updated on 27-Mar-2018
DIVERGENCE, RELATIVE HUMIDITY, WINDS AND OMEGAS
(VERTICAL CROSS/TIME SECTIONS)

Macro/script designed to evaluate the vertical structure of convergence and divergence, and its relation with vertical motion and saturation. It includes horizontal winds [kt] and vertical motion (arrows). It is used at the tropical desk on a daily basis to evaluate the potential for moist convection enhanced by atmospheric dynamics.
This macro needs to go inside your "C:/WINGRIDDS/MACROS/" folder. Note: Requires the ALIAS.USR but does NOT require a color table.




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Page last modified: Wednesday, 28-Mar-2018 13:55:51 UTC