Principal Investigator: Sim D. Aberson

Objective: Evaluation of methods to provide estimates of model error in operational forecasts of tropical cyclone motion.
Rationale: Recent years have shown a slow and steady increase in skill of operational tropical cyclone track forecasts. A number of operational track forecast models have average skill approaching 40%, yet none of them performs well consistently, and a serious challenge for operational forecasters is to choose which of the various possibilities presented by the ensemble of different models is the most likely to occur. Not only should the guidance itself be presented to forecasters, but an estimate of the confidence which should be placed in that forecast as well. Thus, a method for the Prediction of Model Performance (POMP), and methods in ensemble forecasting are studied.
Method: A method to objectively estimate the confidence in track forecasts has been developed for the ensemble of models currently in use. Data from the synoptic situation in the environment of each tropical cyclone, climatological data, and past performance of each model are analyzed from the 1989 - 1995 hurricane seasons to allow a linear discriminant analysis to differentiate between forecasts which are expected to perform well from those expected to be poor, giving the forecasters an object estimate of confidence of the individual forecasts. (Fig. 1)

Accomplishment: The linear discriminant analysis for the HRD VICBAR model has shown that individual forecasts which are expected to be poor can be differentiated from those expected to be good, allowing forecasters to disregard the expected-poor information and improve their forecasts. Since the ensemble mean forecasts are, on average, better than forecasts from individual models, this information can be used to provide weighted-ensemble mean predictions to forecasters.

The following manuscript has been submitted for publication: Aberson, S. D., 1997: Five day tropical cyclone track forecasts in the North Atlantic basin. Submitted to Wea. Forecasting.

Key references:

Aberson, S. D., and M. DeMaria, 1994: Verification of a nested barotropic hurricane track forecast model (VICBAR). Mon. Wea. Rev., 122, 2804-2815.

Aberson, S. D., 1997: The prediction of the performance of a nested barotropic hurricane track forecast model. Wea. Forecasting, 12, 24-30.

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Last modified: 6/26/97