Cause analysis on a severe convective weather and accompanied short-term heavy rainfall

Based on conventional surface data,upper-air observation,automatic station,NCEP reanalysis,Doppler radar and WRF model simulation data,the characteristics and causes of a severe convective weather process with short-term rainstorm in Shanxi,He'nan,Shandong,Anhui and Jiangsu provinces in the early June,2009 were analyzed. Results show that the severe convective weather occurred under favorable condition of cold and warm air confluence formed by the convergence of the southerly cold air guided by northeast cold vortex at high level with the low vortex disturbance at low level. The strong convergent updraft in boundary layer was one of the main reasons for triggerring the convection and releasing the convective instability energy. Furthermore,the strong potential instability caused by the overlapping of dry intrusion at upper level upon the wet and warm air of the high Potential Vorticity( PV) at lower level provided a favorable condition for the development of the severe convective weather. Moreover,a strong storm relative helicity existed on the side of the movement direction of the convective system,and the tilting effects of updraft air in the low convergence made the horizontal vorticity transform in-to the vertical one,which all provided a favorable condition for the development and maintaining of this severe convective weather and accompanied short-term rainstorm.