Abstract:Abstract：Using the precipitation data of intensive automatic weather station, ERA5 reanalysis data and radar data, a local rainstorm process influenced by the parallel ridge-valley topography in western Chongqing from 16 to 17 June 2020 is analyzed. The results show that the rainstorm process is happened under the combined influence of the stable low vortex shear formed by the southwest warm and humid low-level airflow around the subtropical high and the northward air flow intruding into the Sichuan Basin under the guidance of the high trough in western Chongqing, and the maintaining mesoscale convergence line under the influence of the parallel ridge-valley topography. From 00:00 to 03:00 UTC 17 June, there are obvious moisture convergence, ascending motion and strong instability center in the boundary layer below 850 hPa in the ridge-valley region, which result in local heavy rainfall. Under the influence of the ridge-valley topography, the cold front and the convergence center moving northward along the convergence line lifts on the windward slope, which strengthen the vertical ascending motion that increase the vertical circulation wind speed in front of the front, which is an important reason for the rainstorm amplification in the southern end of Huaying Mountain and the eastern transition area of wide valleys and hills. The development and evolution of the mesoscale convective systems are closely related to the postion change of the surface convergence line. The convergence listing of the parallel ridge-valley makes the mesoscale convective systems stagnate near the Huaying Mountain and develop and strengthen twice at its southern end.