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Comparison of deterministic forecasts generated by computer models and manual methods

Forecasts from NWP models and human forecasters cannot really be compared, because they have different aims:

  • NWP modellers try to provide forecast systems with optimum accuracy.  Their aim is to model all scales of atmospheric motions, irrespective of whether they are predictable or not. (see Fig6.5.1).
  • Weather forecasters do the opposite. They disregard and dampen down unpredictable features in order to improve accuracy and reduce jumpiness in their categorical forecasts (see Fig6.5.2).


  

 Fig6.5.1: Typical root mean square error and variability of good (blue) and poor (red) high-resolution NWP models.

A good NWP model represents the whole spectrum of resolvable atmospheric scales throughout the forecast.  Thus errors trend towards a higher level but variability remains fairly constant.

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