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
Wind at 850 hPa
This map presents the average wind vector at 850 hPa for every modeled gridpoint
(ca. 80 km). The average pressure altitude for 850 hPa is at about 1500m a.s.l. (5000 ft).
One can read its present altitude from the 'z T 850 hPa' chart. This map is very useful
for gliders and hang-gliders if their airfield or starting pad is significantly below the
850 hPa pressure altitude. (wind-converter
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).