Analysis on a Heavy Rainstorm from Southwest Vortex Moving Toward Northeast Direction in Sichuan and Shaanxi Provinces

The influential systems,upper jet,stream field and convective vorticity vector for a heavy rainstorm impacted southwest vortex in northeast part of Sichuan and southeast part of Shaanxi on 16-19 July 2010 are diagnostically analyzed based on the conventional observation data,NCEP reanalysis data,automatic station data,satellite cloud image and radar data.The results show that the stable saddle field provides the background for the occurring and developing of the southwest vortex and northeastward moving.A deep trough in north and southwest vortex in south pattern is important reason for the southwest vortex to maintain.The division area,which is formed by between the northeast airflow on south side of the northeast-southwest direction upper jet center and the southeast airflow on northeast side of the South Asia high,offers the dynamic condition for ascending motion.The south warm-wet airflow caused by the strong pressure gradient force between typhoon and Subtropical High supplies the abundant water vapor for the heavy rainstorm area.The precipitation intensity caused by southwest vortex during the developing phase is significantly greater than decaying phase.The heavy rainstorm locates in the coincidence area of the vertical component of convective vorticity vector and atmospheric column cloud water.