How does MetService use computers to forecast the weather?
The atmosphere can be thought of as a thin film of fluid covering the Earth’s surface. Its movement, or circulation, is powered by the difference in temperature between the Equator and the Poles, and is influenced by the Earth’s rotation. We may recognise some of these circulations as the high and low pressure systems on a weather map. The motion of the atmosphere can be described mathematically using a Numerical Weather Prediction (NWP) computer model. NWP models work by mapping a mathematical description of the atmosphere onto a three-dimensional computational grid. The state of the atmosphere is then calculated (forecast) at each point on the grid for given steps of time into the future. These time steps are typically of the order of several minutes, while the total time span of the computer forecast may range from one to five days, or more, into the future. A number of weather forecasting agencies operate modelling centres where supercomputers are used to run NWP models that span t
