What is Numerical weather prediction?
{{No sources|date=December 2024}} [[File:GFS 850 MB.PNG|thumb|Numerical weather prediction, using GFS]] '''Numerical weather prediction''' is the way [[weather forecast]]s are made. This is done using [[computer model]]s of the [[atmosphere]]. Such models describe the current weather conditions, and how they change over time using [[equation]]s. Using the current weather conditions, the equations can be solved, or approximated to tell what the weather will be like in the near future. The relevant physical parameters, such as [[pressure]], [[temperature]], the direction and the speed of the [[wind]] are taken to be [[function]]s of [[time]]. These are modelled with a system of [[partial differential equation]]s. This is a [[dynamic system]] that is solved [[number|numerically]]. Most of these equations are implemented using [[FORTRAN]]. The equations are approximated. Since the number of calculations is huge, [[supercomputer]]s usually do them, to finish before it's too late. ==Basic idea== The [[atmosphere]] is modelled as a [[fluid]]. The basic idea of numerical weather prediction is to sample the state of the fluid at a given time. The equations of [[fluid dynamics]] and [[thermodynamics]] can then be used to estimate the state of the fluid at some time in the future. ==Local weather prediction== The results are usually too inaccurate to be used for predicting the weather at any place. For this reason, [[meteorologist]]s check the values, and compare them to historical data. In other words, they use the data to help produce the weather forecast. [[Model Output Statistics]] is a [[statistics|statistical]] model that was developed in the 1960s and 1970s. It uses [[regression analysis]] for a fully automated forecast. With it, historical data is analysed automatically. One of its applications is called Direct Model Output. MOS uses both historical data and statistical modeling. Predictions beyond about six hours are unreliable. Another well-known model is called [[Global Forecast System]] (GFS), which is run