Abstract:Bilis(0604),Kaemi(0605) and Sepat(0709) have the serious disaster effect on Hunan province. Numerical experiments were conducted on three landfall tropical cyclones (TCs) by use of mesoscale model (GRAPES2.5). Verified against observations, the tracks and detailed mesoscale precipitation distributions were well reproduced. Based on reliable outputs of 1h factor, the moist potential vorticity (MPV) was analyzed. It is found that MPV is an evident predictor of heavy rains, the corresponding relation between the negative center of MPV and heavy rain area was better, and the absolute value variation of MPV had positive correlation to the intensitiy of one hour precipitation, during 05:00~08,July 15,113mm/3h,while MPV reaches its maximum of 120 PVU,followed by consistent weakening of them both.