The newly modified 1997 version of the Typhoon Track Forecast System (TFS) of the Central Weather Bureau (CWB) in Taiwan had made significant improvement on typhoon track forecast (Huang et al., 1998). The mean 48-h distance forecast error has decreased from 338 km in 1996 typhoon season to 264 km in 1997. Some changes, mainly on model initialization processes, have been made during the upgrade from the 1996 version to the 1997 version. It is still under investigation whether the improvement of the model track forecasts was really due to the change in the initialization procedures, and how sensitive the track forecasts respond to different initial conditions.
Meanwhile, potential vorticity (PV) analysis (Wu and Emanuel, 1995) is being carried out. It is hoped that the major PV characteristics associated with different track patterns can be identified. Some of these findings can be useful for developing a better strategy for operational ensemble forecasts.