Model:

Updated:

4 times per day, from 00:00, 06:00, 12:00 and 18:00 UTC

Greenwich Mean Time:

12:00 UTC = 07:00 EST

Resolution:

0.25° x 0.25°

Parameter:

Sea Level Pressure in hPa (solid lines) and equivalent potential temperature at 850 hPa (dashed and coloured)

Description:

The equivalent potential temperature is calculated from the specific humidity (ratio of mass of the water vapor to the total mass of the system) and the temperature, both at 850 hPa. Therefore, from this map one can read the fronts even better than from the 'RH 700 hPa' or other maps.

GDAS

The Global Data Assimilation System (GDAS) is the system used by the National Center for Environmental Prediction (NCEP) Global Forecast System (GFS) model to place observations into a gridded model space for the purpose of starting, or initializing, weather forecasts with observed data. GDAS adds the following types of observations to a gridded, 3-D, model space: surface observations, balloon data, wind profiler data, aircraft reports, buoy observations, radar observations, and satellite observations.

NWP:

Numerical weather prediction uses current weather conditions as input into mathematical models of the atmosphere to predict the weather. Although the first efforts to accomplish this were done in the 1920s, it wasn't until the advent of the computer and computer simulation that it was feasible to do in real-time. Manipulating the huge datasets and performing the complex calculations necessary to do this on a resolution fine enough to make the results useful requires the use of some of the most powerful supercomputers in the world. A number of forecast models, both global and regional in scale, are run to help create forecasts for nations worldwide. Use of model ensemble forecasts helps to define the forecast uncertainty and extend weather forecasting farther into the future than would otherwise be possible.

Wikipedia, Numerical weather prediction, http://en.wikipedia.org/wiki/Numerical_weather_prediction(as of Feb. 9, 2010, 20:50 UTC).