Abstract -- Purpose of this project is to analyze those typhoons accompanied with northeast monsoon, to understand the mechanism leading to heavy rainfall and to develop the forecast guidance for heavy rainfall. Results showed that there were 13 typhoons affecting Taiwan during the fall (consider only October and November) of 1986-2000. Among these typhoons, six were considered to have significant interactions with northeast monsoon after analyzing their tracks, synoptic patterns and the rainfall distributions. These six typhoons appeared to have similar synoptic environment and experienced two different types of track. One was moving westward across the Bashi Channel and the other moving northward to the east of Taiwan. The rainfall distribution estimated by the climatological model of typhoon rainfall (Lee et al.,2002) tended to underestimate seriously the rainfall amount at the northern and northeastern coastal regions for these typhoons. For those typhoons not interacting with northeast monsoon, the underestimate was not so serious.
Results also showed that MM5 could simulate reasonably well the track, synoptic pattern and most of the rainfall distribution during the period when Lynn (1986) was influencing Taiwan. Unfortunately, some major rainfall area occurred to the north of Taiwan due to small errors in simulated wind field. Currently, detail analysis of the simulated results and a sensitivity run without Taiwan terrain are undergoing.