An analysis of the heavy rain under the background of the sitzkrieg between Subtropical High and cold front

By using the synoptic chart, densified observation of precipitation and sounding data, the meteorological causes of the heavy rain which occurred from Jul 21 to 23 in 2009 over Changjiang-Huaihe river valley are analyzed. Results demonstrate that the cross swords between subtropical High and cold front is the main cause for this heavy rain. The Changjiang-Huaihe river valley lie in markedly moist region. The temperature over Changjiang-Huaihe river valley at 700 hPa is reduced significantly. Shear lines at 850 and 700 hPa are maintained for long time over Changjiang-Huaihe river valley. The surface cold front moved cross this region. The area of heavy rain moved with the convergence line. As the slow movement of Subtropical High, sitzkrieg between Subtropical High and cold front is maintained over Changjiang-Huaihe river valley for long time, the heavy rain is maintained consequently for long time.