ECMWF: Global weather forecast model from the "European Centre for Medium-Range Weather Forecasts"
2 times per day, from 10:00 and 23:00 UTC
Greenwich Mean Time:
12:00 UTC = 12:00 GMT
Geopotential height Temperature at 500 hPa
Geopotential height at 500 hPa (solid line)
Temperature at 500 hPa (colored, dashed)
The maps show the predominant tropospheric waves (trough or ridge).
They virtually control the ''weather'' (dry, warm / wet, cold) and the long waves
drive the smaller synoptic waves.
Thus, this upper-level chart illustrates the dynamics of our atmosphere.
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).