Performance of the Typhoon Forecast System of the Central Weather Bureau in Taiwan

There are 21 typhoons happened on the northwestern Pacific Ocean and the Southern China Sea in 1999. The average 24/48/72 hours typhoon track forecast errors for the Typhoon Forecast System (TFS) of Central Weather Bureau (CWB) in Taiwan are 150km/270km/503km. The horizontal resolution is 45km and in the vertical, there are 20 levels in the terrain-following sigma coordinate. CWB plan to upgrade the computer hardware from Fujitsu VPP300 to VPP5000 in the end of 1999. The compute speed of VPP5000 is about 4 times faster than VPP300. After the Message Passing Interface (MPI) had been used in TFS, only 127 seconds will cost for 72 hours forecast in VPP5000 (12PE). For the powerful resource, CWB should try to develop the high-resolution Typhoon Forecast System.

In this report, we'll describe the developments and some case studies of the high-resolution TFS (15km, 30 sigma-levels). Several cases had been tested for the new-version TFS shown that the track forecasts will be improved slightly and the structure of vortex also maintained well. Besides that, we plan to rerun more typhoon cases, such as Herb (1996)and Zeb (1997) which had had caused very serious damage to Taiwan. We'll try to analyze the forecast pattern of rainfall and the interactions between typhoon and the topography.