Improvement of a Baroclinic Typhoon Motion Prediction System by Adjustment of the Initial Wind Field

Abstract

Abstract A technique is developed to adjust the initial wind fields of a dynamical tropical cyclone motion forecast model given knowledge of the recent track of the storm. Statistical regression equations are used to estimate the 6 h storm motion from the initial steering currents in the three-layer, primitive equation model. The difference between the actual and predicted storm motion after 6 h is used to adjust the initial wind fields near the center. The region of maximum adjustment is placed at four grid points (about 6° latitude) from the center of the storm. Relative magnitudes of the adjustment of the zonal versus the meridional component are determined by trial and error. The adjustment technique is tested with seven hand-analyzed and 23 operationally analyzed cases. In both groups, the initial wind field adjustment decreases significantly the errors for the dynamical model forecasts. With the operationally analyzed cases the improvement of about 30% during the first 18 h resulted in motion foreca...