Explanation of USA Forecast Maps

1. Finding Your Forecast on the Web Page

These USA forecast products are currently a limited set of tropospheric forecasts targeted for various flight and gliding applications. 

Table 1. Explanation of the forecast table entries and hyperlinks

The way to interpret the table entries on the USA forecasts page is depicted opposite. There are two types of MWFM forecast maps that can be viewed by clicking the relevant table entry. The standard model forecast (MWFM 1.0) for the eastern USA (EUSA) and western USA (WUSA) is provided with simple maps that provide plots with either black or white backgrounds: click on the relevant WUSA, EUSA, WUSA or EUSA table entry and the forecast map will be displayed (see Table 1). The new "next generation" model (MWFM 2.0) forecasts are given by clicking on the red MWFM 2.0 hyperlinks (Table 1), and provide a single map for the entire continental USA. 

Table rows are color coded according to the source of global forecast winds and temperatures used in each case. Two different sources are being used at present (see below). This is done to: (a) ensure at least one MWFM forecast exists at any given time; (b) allow consistency checks, since sometimes the forecasts can vary due to different large-scale forecasting predictions; (c) provide a primitive kind of "ensemble" mountain wave forecast based on forecasts of different large-scale models. 

These MWFM forecasts are based on global forecast data from the National Centers for Environmental Prediction (NCEP). These NCEP-initialized MWFM forecasts are run every day at NRL-DC at ~04:00 & 06:30 EST (~08:00 & 10:30 UT), times when output from NCEP's "AVN" (Aviation Model) and "MRF" (Medium Range Forecast) runs generally come online. The algorithm searches for both AVN and MRF output each time, and opts for MRF in both are present. Both MRF and AVN fields are gridded at 1^ox1^o from 1000-10 hPa, based on T170L42 model runs.

1.2 Forecasts Using NOGAPS-initialized Fields 

These MWFM forecasts are based on global forecast data from the Navy Operational Global Analysis and Prediction System (NOGAPS), provided by NRL's Marine Meteorology Division in Monterey, California. These NOGAPS-initialized MWFM forecasts are run every day at NRL-DC at ~13:15 EST (~17:15 UT). These NOGAPS input fields are T159L24 forecast runs output on 1^ox1^o grids from 1000-10 hPa.

NCEP and NOGAPS forecasts are easily located in the MWFM forecast tables since their table entries are color coded orange and pink, respectively. 

2. Forecast Products

2.1 Vertical Displacements

2.2 Mountain Wave-Induced Turbulence

3. MWFM 1.0 Maps

MWFM 1.0 maps are forecasts produced by the MWFM 1.0 hydrostatic mountain wave forecasting algorithm, a basic description of which can be found here. The "boxes" in the forecast maps correspond to "ridge elements" from our idealized mathematical decomposition of the dominant ridge features in the Earth's topography. In the MWFM 1.0 model, mountain waves always propagate vertically above the ridge feature that forced them. Thus, the forecast maps come plotted as color coded ridge feature, which identifies the parent orography associated with this vertically propagating mountain wave. The color code corresponds to the intensity of the quantity (vertical displacement, turbulence, etc..) associated with the mountain wave launched from this ridge feature. Two types of forecasting maps are provided: both plot identical information, but use different color schemes. Blue contours show geopotential heights (similar to lows/highs on weather map, with winds blowing roughly parallel to the contour lines).

3.1 Black Background (Screen Friendly)

These plots are the basic forecasting maps that have been issued for many years. They are retained for reasons of heritage and backwards-compatibility, and also  because some people still prefer them to the newer plot formats. They're nice to look at on a browser, but clearly aren't ideal to print out on a color printer. These plots are good for identifying large-amplitude active regions.

3.2 White Background (Printer Friendly)

These are identical plots to the black background ones, but the white background makes them more amenable to printing on both color and black-and-white plotters/printers. The eye also seems to resolve more low-amplitude structure in these plots, and thus these plots are good for identifying full distributions of all mountain wave activity.

4. MWFM 2.0 Maps

Since the MWFM 2.0 model is quite a bit different to MWFM 1.0, we have developed entirely new plot routines for displaying these forecasts. Blue is ocean, while underlying land is plotted with a gray-scale, with light gray indicating high mountains and dark gray the low-lying terrain and plains. Forecast mountain wave activity is plotted using a red-yellow color scale. Each red-yellow "fleck" on the plot corresponds to the phase line of the forecast mountain wave "ray." For instance, linear cloud bands would form along these phase lines if the waves in question produced regional cloud banding. Unlike MWFM 1.0, waves in the MWFM 2.0 can propagate away from the mountain, and so a more continuous distribution of activity results both above and downstream of the parent ridge. Green arrows show the wind vectors at the altitude in question. Aqua dotted contours show geopotential heights (similar to lows/highs on weather map, with winds blowing roughly parallel to the contour lines). Printer-friendly versions can be generated on request.

4.1 MWFM 2.0 Forecast Maps

These are the new forecast maps for the entire USA generated using results from "next generation" MWFM 2.0 forecasting algorithm for entire continental USA.

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