Model:

Ververst:

2 times per day, from 10:00 and 23:00 UTC

Greenwich Mean Time:

12:00 UTC = 13:00 MET

Resolutie:

1.0° x 1.0°

Parameter:

Maximum wind velocity of convective wind gusts

Beschrijving:

The method of Ivens (1987) is used by the forecasters at KNMI to predict the
maximum wind velocity associated with heavy showers or thunderstorms. The
method of Ivens is based on two multiple regression equations that were
derived using about 120 summertime cases (April to September) between 1980 and 1983.
The upper-air data were derived from the soundings at De Bilt, and
observations of
thunder by synop stations were used as an indicator of the presence of
convection.
The regression equations for the maximum wind velocity (w_{max} ) in m/s
according
to Ivens (1987) are:

where

- if T
_{x}- θ_{w850}< 9°C- w
_{max}= 7.66 + 0.653⋅(θ_{w850}- θ_{w500}) + 0.976⋅U_{850}

- w
- if T
_{x}- θ_{w850}≥ 9° C - w
_{max}= 8.17 + 0.473⋅(θ_{w850}- θ_{w500}) + (0.174⋅U_{850}+ 0.057⋅U_{250})⋅√(T_{x}- θ_{w850})

where

- T
_{x}is the maximum day-time temperature at 2 m in K - θ
_{wxxx}the potential wet-bulb temperature at xxx hPa in K - U
_{xxx}the wind velocity at xxx hPa in m/s.

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).

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