Abstract:Using high resolution prediction field (0.25°×0.25°) data of European Centre for Medium Range Weather Forecasts (ECMWF) and the data of encrypted automatic stations of Sichuan Province, 20 cases of heavy rainfall indexes for moist helicity in flood season from July to September 2011 and May to July 2012 were analyzed by the statistical method, including the moist helicity indexes of the occurrence, development and falling area distribution of 6 h, 24 h severe precipitation. Two cases of severe precipitation process and all heavy rainfalls in Sichuan Basin during the 2013 flood season were checked out by using these criteria and put into the forecasting operation in the flood season. The results show that the distribution of 700 or 850 hPa moisture helicity can give good indicator to the distribution of rainfalls. When extremely heavy rainfall occurs, moist helicity values exceed the index values two times or more in the 24 h forecast, with 3 h interval forecasting field, meeting the requirments of severe precipitation occurrence. In zero field prediction of the 24 h forecast with 3 h interval forecasting field. The moist helicity number at any time reaches the 6 h criterion value, which has instructive effect on subsequent 6 h rainfall area and can be used as a short time nowcasting reference. TS score for corrected moist helicity is higher than ECMWF model and has a good forecast effect.