Experiments in Barotropic Hurricane Track Forecasting

Abstract

The barotropic prediction model, applied in a way appropriate to the character of tropical circulations and of the information available to describe them, is found to be capable of providing a basis for a significant advance of the state of the art of hurricane track forecasting in the range from 24?72 hr in regions of relatively dense rawinsonde data coverage. The distinctive features of the technique are application of the barotropic equation to tropospheric mean data computed from information at 10 constant-pressure levels, prognostic use of a stream function derived from direct analysis of the mean wind field, and numerical calculation over a grid with relatively small mesh length, without separation of the tropical vortex from the residual flow. A series of test forecasts for hurricanes Donna 1960, Carla 1961, and Flora 1963 illustrates the performance of the model in dealing with storms characterized by a wide variety of behavior. The most prominent failure, a premature forecast of the recurvature of Donna, is found to be attributable to the baroclinic filling of a trough off the east coast of the United States.