Abstract: Using MM4 (PSU/NCAR) model, the torrential rain process of typhoon from 2000 BT. August 31 to 2000 BT. Sept. 1, 1992 was simulated and studied. The results show that the typhoon discontinuous northerly jump was related to the westerly trough and the feedback of cumulus convection latent heating, and the development of cumulus convection in the south rain area of inverted trough enhanced the transporting for the water vapor, momentum and heat from south to north. These processes would cause a great increasing of precipitation. The feedback of cumulus convection latent heating affects greatly the upper and lower level jets and the motion of the typhoon.