The Features of a Severe Torrential Rain Caused by Southwest Vortex in Northeast Sichuan Basin in Autumn

Based on the intensive meteorological observation stations data,sounding data,and FY-2E Satellite cloud images,the persistent and severe rainstorm process which occurred in northeast Sichuan Basin from 13 to 14 September 2014 was analyzed. The results show that:(1) This rainfall occurred in the stable circulation of eastern Asian,with East high and West low,northeast of Sichuan Basin located in southerly side of upper-level westerly jet and northerly side of upper-level easterly jet of branch,it is conducive to development. The key of northeast Sichuan heavy rainstorm process is the maintenance of the SW vortex at Sichuan Basin long time. The formation of the surface wind direction shear has certain significance to the rainstorm.(2) the extremely heavy rainstorm is caused by mesoscale convective systems(MCS),which continual appearing and disappearing in the Southwest Vortex weather system. MCS cloud development to the mature stage,move slowing,cold cloud center TBB values below 72 degrees. There are many mesoscale rain cluster,and there are two or more short-term strong precipitation peaks in each heavy rainfall period.(3) In the precipitation process,Shapingba station sounding data is more reference value for this strong precipitation at 13,One of the features revealed is that a V-shape separation occurs between the stratification curve and the dew point profiles,this shape is benefit to severe convective weather.