Abstract:Using conventional weather data, FY-2E satellite data, Doppler radar products, lightning location data, automatic weather station data, this paper analyzes the 4 April 2015 evening to night thunderstorm gale process in Sichuan Basin. Our analysis shows that the thunderstorm gale process was formed by the cold front forced uplift on warm air mass as well as dry and cold air into the warm area. The area of hollow dry layer, large temperature lapse rate, coupling of high low jet area and the low level temperature near the ridge were conducive to the potential area of extreme thunderstorm gale. This area provided a favorable environmental condition for the thunderstorm such as significant unstable conditions, water vapor, dynamic uplift, etc. Cold air firstly invaded from the middle and lower layers of the northwestern part of the basin and triggered a series of thunderstorm cells on the low level shear line, which developed rapidly in the most favorable area for the development of convection. The interaction of the mesoscale vortex, the front inflow and the posterior inflow into the northern part of the latent region led to the formation of a single bow echo, which had much higher reflectivity and liquid water content than ordinary thunderstorm. According to the development characteristics of radar echo, the extreme gale was caused by the wet downburst brought by single bow ech. The descending height of the high reflectivity factor in the bow echo means that the sinking air stream was accompanied by a drop in precipitation particles. The dry air was trapped in the sinking air stream and raindrops evaporated quickly, greatly increasing the intensity of the sinking air stream, and thus increasing the strength of the gale. Our analysis also indicates that, by analyzing the background conditions of convective development, forecasters could identify the potential regions for the most favorable convective development paying close attention to the location of the trigger conditions and the characteristics of the radar echo shape as well as the evolution characteristics in the region could be helpful for the early warning of gale weather.