On 30-31 August 2002, a modest mid-latitude trough system moved over the north of Korean peninsula and a typhoon came from the south of the peninsula. The east coast of the middle part of the peninsula in latitude was devastated by the typhoon, mainly due to the unexpected heavy rainfall. Especially in Gangneung area, a daily precipitation reached 870.5 mm/day in 31 August. At rainfall episode, there were two precipitation peaks. For the two peaks of hourly amounts of rainfall, We have confirmed that the first event was occurred by mid-level frontogenesis developed between the typhoon and mid-latitude trough. The frontogenetical forcing together with secondary circulation is discussed to cause the intense precipitation over that region.

In our study we found evidences that the interaction between the typhoon and upper-level trough, though not in mature phase, can intensify the above upper-level frontogenesis Each frontogenetical forcing was analyzed both at the 500-hpa level and at vertical cross-frontal face. In our analysis, horizontal deformation forcing was the most efficient factor to generate mid-level front. Diabatic and tilt forcing which was developed just after initiation of precipitation complimented each other, so they didn't contribute much frontogenesis. Moreover, applying Sawyer-Eliassen equation to the simulated frontal zone, we confirmed that the front was key mechanism in bring out strong convection causing heavy rainfall.

In conclusion, the interaction between typhoon vortex and mid-latitude mobile trough generated horizontal deformation field at mid level, which causes strong temperature gradient at the same level at the slightly north of Gangneung area. The intense heavy rainfall, consequently, existed at the ascent region of secondary circulation forced by the front.