Abstract:

Based on MICAPS3 data, a local short-time severe rainstorm occurred on July 1-2, 2013 in the eastern area of Jinzhou was analyzed using a V-3θ chart method. The results show that this process occurs under the background of northeast cold vortex. In general, it is difficult to forecast a local short-time rainstorm by the conventional synoptic analysis, while a structure analysis method of the V-3θ chart using inhomogeneity and discontinuity of significant pressure layer could reflect vertical motivation of vortex. Thus, it could make up deficiency of conventional rainstorm forecasting. There exists ultra-low temperature on the V-3θ chart in Jinzhou and its upper reaches area before previous 12 to 24 hours of local short-time rainstorm. From the start to the end of this process, tumble is changed from “clockwise” to “anti-clockwise”. Curves of θ, θsed and θ* are changed from left incline in many points to gradual right incline, and instability energy gradually reduces. Water vapor invades from dry layer to wet layer, and then the whole layer changes wet layer. At last, the whole layer becomes dry layer. The above characters mentioned could be of indicative to a local short-time rainstorm in Jinzhou area. Analysis of radar velocity is favorable to judge wind speed and wind direction at different heights, and then judge the “tumble effect”, which can make up shortcomings of low space-time resolution of V-3θ chart. Also, different distribution of underlying surface could change wind speed and wind direction, and further influences "tumble effect”, so this is an important basis for falling area of local short-time rainstorm.

Key words:  V-3&theta, chart, Local short-time rainstorm, Ultra-low temperature, Tumble effect