Abstract: Large and meso scale analyses are made for extremely heavy rain and meso-β scale low vortex occurring in Jiading of Shanghai during 6-7 July, 2001. It is shown that extremely heavy rain happened for the instance of interaction among inverted typhoon trough and westerly troug hand continent cold high and west Pacific Ocean subtropical high, especially for the instance of westerly trough linking toget her with inverted typhoon trough at northwest side of west Pacific Ocean subtropical high. Numerical simulation is made using a 21-level improved REM model for this course. The model is that we improved using vertical varying distance difference scheme and Blackadar high resolution PBL scheme and improved its horizontal resolution from 1°×1° to 0.25°×0.25°, etc. The model uses Egrid, and Betts convective parameterized scheme. The terrain is made using Wallace envelope topography. The simulation shows that, not only the typhoon center and the inverted trough are well simulated, but also the extremely heavy rain and meso-scale low vortex. The nort heast to southwest forecast rain area is similar to observation, only the forecast extremely heavy rain center is located sout heast far about 30km from observation.