Operational Prediction of Typhoon Track at KMA using Barotropic Adaptive-grid Typhoon Simulation (BATS) Model

[摘要] Since the adoption of the barotropic adaptive-grid typhoon simulation model in the KMA numerical weather prediction system in 1997, the model has been increasingly recognized to be quite useful in forecasting tropical cyclone tracks. This paper presents the description of the model and history of the model upgrades and the corresponding performance in track predictions of tropical cyclones. There have been two major model upgrades. The first upgrade is on the modification of the steering current. The model is run for 12 hours to catch the initial tendency of the vortex motion in the model and evaluate its departure from the observed one. The vector difference is added to the original steering current and then the model is rerun using the modified steering current. The improvement is mainly for the short-term forecast. Secondly, we let the circular bogus area vary with respect to the 30 kt wind radius (referred to as the storm size) reported from the RSMC Tokyo. For tropical cyclones whose size is larger than 440 km we let the circular bogus area of 1.2 times the 30 kt wind radius from the RSMC tropical cyclone bulletin. For storms smaller than 440 km, we use a constant bogus area of 600 km radius. This provides us a great improvement over the incumbent operational version of the model. The improvement ranges from at least 10% and up to 15% during the entire forecast period of 60 hours.

[学科分类] 大气科学