Analysis of Mesoscale Characteristics of a Torrential Rain in Hubei Province

Based on various conventional and unconventional data, precipitation characteristics, generation and development of the mesoscale convective system and environment conditions of the torrential rain in Hubei Province during 18th and 20th July 2016 were analyzed in this paper. It was found this torrential rain process was highly extreme. The process consisted of warm area precipitation in the south of Meiyu front and Meiyu frontal precipitation. There was extreme water vapor condition in the two periods. In the first stage, the strong storm has the characteristics of stable and merging of new upstream monomers. Maybe affected by the northerly outflow of the storm, the wind on the ground near the Maliang station turned into northeast wind, which formed a convergence with the southeast wind on the south side, and continuously initiated new monomers in the upper reaches of the strong echo. Affected by the southwest guiding airflow, the monomers moved into the strong storm. In the strong stage, the vertical wind shear increased, which was beneficial to the appearance of mesocyclone structure. In the second stage, the parallel layered MCS distributed in the northeast-southwest direction, which had the characteristics of multiple monomers arranging in sequence.The nascent monomer continuously generated affected by the ground convergence line on the southwest side of the system. They moved northeast,which made the parallel layered MCS enhanced and maintained. Later, the invasion of cold air near the ground accelerated the eastward migration of the main echo of parallel layered MCS, resulting in the separation of the main echo from the new monomer and the rapid weakening and dissipation of the system.