Study on the Prediction of Summer Rainstorm Caused by Southwest Vortex

[Objective] The aim was to study the prediction of summer rainstorm caused by southwest vortex.[Method] Based on 2.5°×2.5° reanalysis data in four hours a day from June to August during 1971-2008 at 700 hPa in northern hemisphere provided by NECP,rainstorm and southwest vortex from June to August in Guizhou Province were studied systematically,and the forecast idea of rainstorm caused by southwest was obtained.[Result] Southwest vortex was one of major influence systems of rainstorm in flood season(from June to August),especially in June and July;the occurrence of this kind of rainstorm was closely related to the moving path of southwest vortex,activity of cold air,environmental flow filed at 500 hPa,shear line at 850 hPa,southwest jet,position of subtropical high ridge,water vapour conditions,vorticity filed,etc.On the basis of factual data,objective forecast system was established and verified by means of similar method and physical diagnosis.The results showed that it was rational to choose upper trough,southwest vortex,conditions of vertical movement,southwest jet,water vapour conditions,etc.as forecast factors;when the center of southwest vortex was located in major key area(100°-105° E,25°-35° N) and secondary key area(105°-108 ° E,25°-35° N),regional rainstorm occurred most easily,especially in major key area with high frequency of rainstorm.[Conclusion] The study could provide references for the improvement of prediction level of rainstorm caused by southwest vortex,disaster prevention and reduction.