Abstract: Based on the data from the automatic weather stations, the conventional observation data, the data from the satellite cloud imagery and the Doppler radar, a rainstorm process on July 31, 2011 in the west of Heilongjiang province was analyzed synthetically. The results show that the rainstorm falling areas are located in the left side of the upper-level westerly jet exit region and the ultral-low-level jet. The upper divergence and lower convergence, the low-level and ultra-low-level jets provide the dynamic conditions and the water vapor conditions for this process, respectively. The
strong dry cold air invades in the middle level of troposphere. The falling area of short-time rainstorm is located in the dry intrusion boundary of the strong cold air in the middle level, and it has a very good corresponding relation with the TBB region of big grads. However, it is near the discontinuity line of wind field on the radar echo velocity chart.

Key words: Rainstorm, Dry intrusion boundary, TBB, Wind field discontinuity line