Performance of the ECMWF model in forecasting the tracks of tropical cyclones in the South China Sea and parts of the western North Pacific

Abstract

The performance of the European Centre for Medium-Range Forecasts model in forecasting the tracks of tropical cyclones in the South China Sea and parts of the western North Pacific for the years 1991-8 was assessed using 2.5° resolution data transmitted operationally over the WMO Global Telecommunication System. Minimum mean sea level pressure centres were used to identify and track the positions of tropical cyclones, and in 1998 the positions of the centre of maximum 850 hPa relative vorticity were also used. The model's performance was compared with that of subjective forecasts made by the Hong Kong Observatory and with no-skill forecasts as represented by a climatology-persistence method in the 1990s. Significant improvements in the model forecasting of tropical cyclone tracks were identified towards the end of that period. The model mean forecast errors for 24-hour, 48-hour and 72-hour positions were 215 km, 340 km and 453 km in the early 1990s (1991-3) respectively, compared with 155 km, 244 km and 292 km in the late 1990s (1996-8).