Prognostic chart

A prognostic chart is a map displaying the likely weather forecast for a future time. Such charts generated by atmospheric models as output from numerical weather prediction and contain a variety of information such as temperature, wind, precipitation and weather fronts. They can also indicate derived atmospheric fields such as vorticity, stability indices, or frontogenesis. Forecast errors need to be taken into account and can be determined either via absolute error, or by considering persistence and absolute error combined.

Definition

The forecast map showing the state of the atmosphere at a future time is called a prognostic chart. Prognostic charts generated by computer models are sometimes referred to as machine-made forecasts.

Variety

Surface weather prognostic charts for mariners indicate the positions of high and low pressure areas, as well as frontal zones, up to five days into the future. Surface wind direction and speed is also forecast on this type of chart. Wave prognostic charts show the expected sea state at some future time. Low-level prognostic charts used by aviators show the forecast between the Earth's surface and 24,000 feet (7,300 m) above sea level over the next two days. They show areas where visual flight rules are in effect, instrument flight rules are in effect, the height of the freezing level, the location of weather features, and areas of moderate to severe turbulence. Prognostic charts can be made of isentropic surfaces (along a certain potential temperature surface determined in kelvin) in regards to moisture advection, mean temperatures at the surface, mean sea level pressures, and precipitation either for a single day or multiple days. For purposes of severe weather, prognostic charts can be issued to depict current weather watches, convective outlooks for thunderstorms multiple days into the future, and fire weather outlooks.