Abstract:Based on various conventional and unconventional data, precipitation characteristics, generation and development of the mesoscale convective system (MCS) and environment conditions of the torrential rainfall in Hubei Province during 18-20 July 2016 are analyzed in this paper. The results show that this torrential rainfall process was highly extreme. The process consisted of warm area precipitation in the south of Meiyu front and Meiyu frontal precipitation. There were extreme water vapor conditions in the two periods. In the first stage, the primary convective monomers were triggered by the convergence of the ground wind field. The southwest low level jet showed pulsation. The thickening of the wet layer promoted the development of strong thunderstorm. The new monomers formed in the upper reaches of thunderstorms, and rapidly merged into strong thunderstorm. The backward propagation was one of the important reasons for its stable and moveless. In the strong phase, the strong thunderstorm had the characteristics of warm cloud and low center of mass. The configuration of vertical wind shear in the low layer and the northerly outflow of thunderstorm and the appearance of mesocyclone both promoted the upward movement, causing the long-term maintenance of the strong thunderstorm. It caused high intensity precipitation at Maliang Station for several hours. In the second stage, the line-parallel layer-mean wind component was bigger than the line-perpendicular, which promoted the formation of northeast-southwest parallel stratiform MCS. It had the characteristics of multiple monomers arranged in sequence, and the nascent monomers were continuously generated under the effect of the ground convergence line on the southwest side of the system. Their development made the parallel stratiform MCS enhanced and maintained. The Maliang Station was affected by the parallel stratiform MCS convection line and the northwest side layered echo, and the hourly precipitation was significantly weaker than in the first stage.