Short-term heavy precipitation is the most severe weather occurring during the warm season in China. This study examines the small or mesoscale characteristics of short-term heavy precipitation and the three-dimensional wind field configuration in depth, using a heavy precipitation event that occurred in Shanghai on June 29, 2022, as a case study. Utilizing X-band phased array radar(XPAR), S-band dual polarization radar, and ground and sounding data, we explore the mechanisms behind this heavy rainfall and its developmental evolution. The findings are as follows: (1) The event was a rainstorm that formed in the warm sector before the cold front, where shallow cold air from the surface interacted with warm, humid airflow, creating a mesoscale convergence line that triggered convection. (2) During this heavy precipitation, radar echoes experienced three mergers and enhancements. The first merger increased echo intensity. The second merger produced multiple cells moving southeast. Sinking airflow from these cells intensified southward surface airflow, continuously generating new units at the southern edge of the storm. After the third merger, the resulting units migrated northeast, with outflow from the storm sustaining northern surface airflow and creating new units on the southern side of the echo. (3) The strengthening of southwest winds and the weakening of northerly airflow led to a rapid decline in radar echo intensity, signaling the end of this short-term heavy precipitation event.