Abstract: Using the data of the high and the ground observation and the reanalysis data of NCEP and T639,this paper comprehensively analyzed the characteristics of weather,the conditions of water vapor,the dynamic conditions and the unstable conditions of the rare heavy rain process of Korla City,Xinjiang,China on June 4^th,2012, and the characteristics of the radar echo and the mesoscale cloud of the heavy rain process. Results show that in most southern Xinjiang area,T-T_d was lower than 4℃ before precipitation,and the area was covered by high humidity,which was resulted from the indirectly transported vapor from Bay of Bengal;the index K was greater than 25 in Korla,providing favorable conditions for the convective weather; Central Asia low slotted into the South Xinjiang Basin and cold air intruded in the middle of its back,these three air flows converged around Korla, and produced strong local upward movement with the extraction effect of high altitude jet stream,and the air lifting effect of the windward side of mountain,which was the main original reason of the heavy rain. The intensity of weather radar echo(PPI) on the drawing had obviously "T" shape glyph radar echo; along the line of "T", there were many medium and small scale convective clouds in glyph echo,and had a short cyclonic convergence keep fit in the low-level development;rainstorm center appeared on the edge of satellite cloud,and the change of the intensity was consistent with the strength of the precipitation. The center of the vertical spiral degree had a good indication to the evolution of the weather system and the area of heavy rain fall.

Key words: rainstorm, "T", shaped radar echo, vertical spiral, water vapor