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Keywords:

  • forecast quality;
  • aeronautical meteorology;
  • verification method;
  • contingency tables

Abstract

Terminal aerodrome forecasts (TAFs) are widely used meteorological forecasts for flight planning. Therefore, there is considerable interest in assessing their accuracy, skill and value. TAFs give information about the expected conditions of wind, visibility, significant weather and clouds at airports. Using different types of change groups, the forecaster gives a range of possible values valid for a time interval, the shortest interval being 1 h. A TAF thus contains a range of forecast conditions for each hour.

Point verification has proved to be difficult for TAFs. To ease these difficulties, time and meteorological state constraints are relaxed in the method described in this paper. This is done by verifying two conditions for each hour of the TAF. The highest (or most favourable) observed value is used to score the highest forecast value, and the lowest (or most adverse) observed value is used to score the lowest forecast value. Entries are made accordingly into two contingency tables. The contingency tables are specific for weather element and lead time.

Verification results should give feedback to forecasters. Contingency tables show the strengths and weaknesses of TAF, and displays for individual TAFs are available in the sense of ‘eyeball verification’. For management information, common verification measures for categorical events (such as the Gerrity Score and the Heidke Skill Score) are calculated from the contingency tables. For answering specific customer questions, verification results in respect to certain values of weather elements are available. Copyright © 2008 Royal Meteorological Society