Abstract:In this paper, a most severe Meiyu front heavy rainfall was analyzed by use of the satellite imagery, Doppler radar and ground based observations data, and the characteristics at different scales of the this weather system were revealed.The results are summarized as follows: (1) This process is an atypical Meiyu front convective storm, with the Baikal blocking high as background conditions. (2) Synoptic scale high altitude trough, southwest vortex, low level jet and ground cyclone provided the heavy rainfall with strong impetus and moisture conditions. (3) On meso α scale, the vertical structure of the storm system was the strong low level convergence and upper level divergence, with a strong updraft in its center. At the same time, in the high level, on the north side of the system there was a high altitude jet which forces to produce a secondary circulation. And the secondary circulation of ascending branch, caused by jetstream of many mesoscale vortices on ground, provides the heavy rainfall with persistently necessary power, water vapor and unstable conditions. (4) There was an evolution of MCS on the cloud imagery. The “counter wind zone” and mesocyclone on the speed map corresponding to the bow echo of radar were just the meso γ system of tornadoes leading to the short term heavy rainfall.