The performance of a typhoon track prediction model with cumulus parameterization

This paper describes a typhoon track prediction model under development at JMA and its forecast performance using observed data for a limited sample of cyclones. The experimental model uses primitive equations in σ coordinate. The model utilizes a limited area grid and is nested in a one-way sense to the forecasts of a hemispheric model. It has a uniform grid system with a horizontal resolution of about 50km and 8 vertical levels and covers the area of 4000km×4000km. The cumulus convective process is parameterized using Kuo's framework. The numerical schemes are specially tuned to realistically maintain the model typhoon. The initial condition consists of a well-formed model typhoon superposed upon a large-scale objective analysis. This model predicts the central pressures and movements of several typhoons observed in 1985 with a fairly good skill. In addition, this model simulates a complex rainfall distribution under the existence of a strong interaction between a typhoon and Baiu front quite reasonably as compared with satellite cloud pictures. Some impact studies suggest that particular attention should be paid for the accuracy of the manual analyses and the performance of the hemispheric model (background model), because they have large effects on the track performance of this model.