Diagnosis and forecast analysis of an extra rainstorm event in Henan in early September of 2010

Based on routine meteorological observation data and NCEP 1°×1°reanalysis data,an extra rainstorm event in Henan province from September 6 to 7 in 2010 was analyzed.The results indicate the following.(1) The establishment of high-pressure ridge from SW to NE at east of Ural Mountains guides the high latitude cold air accumulated in Xinjiang area and leads to the formation of a closed cold vortex in the area,and the low trough split off from the closed vortex continuously moves with cold air eastward and meets with the warm and humid air at subtropical edge in Henan province and produces an extra rainstorm.(2) Glide cold trough near Lake Baikal moves eastward and down south,guiding cool air to intrude into the southwest vortex moving along the shear line eastward into the Henan province,leading to the atmospheric baroclinicity enhancement and the vortex development.The middle and low level convergence is significantly strengthened in the north and east Henan province,and the precipitation development is promoted.(3) The subtropical high took on the shape of zones and its ridge line was stable at 26°-27°N.The interaction between southwest warm wet air current at the edge of the subtropical high and southwest vortex in middle level and low level(or the front shear line) is a typical weather situation of this rainstorm in Henan area.In addition,application of forecast model of torrential rain in Henan province and the physical diagnosis method of objective forecast to this rainstorm forecast can better forecast the rainfall area and precipitation magnitude showing the method has a good reference to forecast regional rainstorm and extra rainstorm.