Abstract:Based on the physical mechanism of heavy rain occurrence, a new heavy rain index THWC (temperature, helicity and water condensation) was constructed by using the ingredients based method to diagnose the dynamic, water vapor and unstable conditions signals. The THWC index calculated with NCEP/NCAR reanalysis data was used to diagnose the northward-moving Typhoon Yagi (No.14 in 2018) affec-ting Haihe River Basin. The results indicated that the THWC index is accurate for forecasting the northerly rainstorm location of typhoon and the center magnitude in the following 6 hours. Then the universality of THWC index was tested according to the northward-moving typhoons affecting Haihe River Basin du-ring 2012-2018. The results showed that the standardized ZTHWC index is more universal than the THWC index, and it has solved unstable problem of THWC index in forecasting quantitative prediction of the central precipitation magnitude. The ZTHWC index has a good correspondence with the main rainstorm location near typhoon center and the central precipitation magnitude in the following 6 hours. The more integrated the atmospheric circulation of northward-moving typhoon is, the better coincidence between ZTHWC and the typhoon main rainstorm area is. Therefore, the ZTHWC index can be used as a quantitative index for forecasting the main rainstorm of the northward-moving typhoon.