An Analysis of the Track and Intensity Errors of Operational Global and Regional Models

For several years, NCEP has been producing tropical cyclone forecast tracks from the output of the Aviation (AVN) and Medium-Range (MRF) runs of its global spectral model. Recently, the tropical cyclone tracking system used at NCEP has been upgraded to also provide tracks for two of NCEP's regional forecasting models, the Eta model and the Nested Grid Model (NGM). In addition, in an effort to begin verifying intensity parameters, the upgraded tracking system also provides the forecasted maximum near-surface winds as well as the forecasted radii of gale-force, storm-force and hurricane-force winds. These forecasted wind parameters, which are sent to the Tropical Prediction Center (TPC) on a real-time basis, are provided for the models listed above as well as for the UKMET and FNMOC/NOGAPS global models.

All forecasted tracks and wind parameters are verified against the operational tropical cyclone data available from TPC. This marks the first time that an objective method has been used to verify tropical cyclone track forecasts for the Eta and NGM models, and it marks the first time that an effort has been made to verify for all these models the specific forecasted wind parameters listed above.

This paper will discuss the details of the new tropical cyclone tracking system used at NCEP, as well as present results for the 1998 and 1999 hurricane seasons for the Atlantic and eastern Pacific basins, specifically: (a) verification of the track forecasts for the various models, (b) verification of the maximum near-surface winds forecasts, (c) verification of the forecasts of the radii of gale-force, storm-force and hurricane-force winds, and (d) a spatial analysis of track error and bias for these models over both basins.