The development of the weather can be modelled by solving equations that describe the atmospheric conditions at a certain point in time in the future. These calculations cover up to 14 days, in some cases even more, and they form the basis of all current weather forecasts.
In the numerical forecast models, the geographical area that is to be covered by the calculations is divided into grid cells. This way, the relevant physical parameters, such as temperature, air pressure, wind direction and wind speed, can be described in three dimensions as a function of time. The physical relations, which describe the status and change of the atmosphere, are modelled as system of partial differential equations. This dynamic system is solved by numerical methods. Since large computer capacity is needed, super computers are often used.
There are several different numerical models available. They all use different methods, resulting in considerable differences in the forecast output. Most of these models are developed for a specific region and describe the rest of the world in a reduced resolution. Generally, the models run at least once a day and offer forecasts for (at least) 00.00 and 12.00 UTC of the days of the forecast period.
In the numerical forecast models, the geographical area that is to be covered by the calculations is divided into grid cells. This way, the relevant physical parameters, such as temperature, air pressure, wind direction and wind speed, can be described in three dimensions as a function of time. The physical relations, which describe the status and change of the atmosphere, are modelled as system of partial differential equations. This dynamic system is solved by numerical methods. Since large computer capacity is needed, super computers are often used.
There are several different numerical models available. They all use different methods, resulting in considerable differences in the forecast output. Most of these models are developed for a specific region and describe the rest of the world in a reduced resolution. Generally, the models run at least once a day and offer forecasts for (at least) 00.00 and 12.00 UTC of the days of the forecast period.