AN EXPERIMENT IN LOW-LATITUDE NUMERICAL PREDICTION WITH THE BAROTROPIC MODEL

Abstract

The experiment consisted of a total of twenty 24-hour numerical forecasts of the 500- and 200-millibar topography, prepared for periods during the spring and summer months. These forecasts, which were made with the barotropic prediction model and the geostrophic approximation, extended well into the tropics in the Caribbean and western Atlantic regions. The problems of upper-air analysis in these areas and the applicability of the barotropic model in low latitudes are considered. Statistical verification of the forecasts and selected examples of the prognostic charts are presented. The results at 500 mb were generally much better than at 200 mb and compare favorably with previous barotropic series. Forecasts were most successful in regions with broad zonal currents, either easterly or westerly, and poorest in the vicinity of the subtropical ridge line. Deficiencies in the predicted motion of synoptic systems were most marked in the vicinity of troughs with sharp curvature and with smaller-scale cyclones and anticyclones. The general results suggest that, at 500 mb, the barotropic model is capable of producing worthwhile predictions of the flow patterns as far south as 15°N.