Analysis on Elevated Thunderstorm Hail in Guangxi in Early Spring of 2012
Based on conventional observational data and radar data, the elevated thunderstorm hail process in Guangxi in early spring of 2012 is analyzed. The results show that: (1) Hail accompanied by thunderstorm occurs on the surface about 1000 km away from the front, and boundary layer is controlled by cold high pressure. The smaller winds at 850 hPa, strong jet stream at 700 hPa and above layer, strong vertical wind shear between 700 hPa and 850 hPa and eastward move of cold trough at 500 hPa provide the trigger condition for the occurrence of the convection. (2) Hail occurs in the range of approximately 200 km away from the shear line at 850 hPa, where there is strong intensity of the pressure surface frontal zone. The negative variable temperature in front of the upper trough increases the temperature difference in vertical direction between 700 hPa and 500 hPa, resulting in the increase of stratification convective instability. When the trough at 500 hPa moves up to the air above the frontal zone, the frontal slope becomes steep, and the upward movement strengthens while the instability increases. All of these make the ice embryo grow in the troposphere and form hail. (3) The storm tracking information displays that storms are generated in high altitudes, and the centroids are 5-6 km high. After the storm is generated, the centroids gradually develop to lower layer with time going. The maximum reflectivity and liquid water content are not large, showing the significant characteristics of the elevated thunderstorms.