Analysis of the splitting processes of the supercell storms based on the Doppler weather radar data

An infrequent process with several supercells generating and splitting at nearby places occurred on 9 July 2007 in the south of the Shijiazhuang region was observed. Based on the Doppler weather radar data from the Xinle station in the Shijiazhuang region, automatic weather station data and conventional weather data, the splitting process and environmental conditions of the splitting supercell storms were analyzed. The results showed that this supercell storm developed under an environmental condition with high convective available potential energy (CAPE) and strong vertical wind shear. Because the direction of vertical wind shear vector rotated counterclockwise with height, after the splitting, the left-moving anticyclonic storms were strengthened and turn into a left-moving supercell storm with deep meso-anticyclone, while the right-moving cyclonic ones were restrained. These results resembled theoretical study. At the same time, it was not in accordance with the theoretical study in some aspects, which include that, the cyclonic storms moving along the warm side of thermal boundary of high humidity region were not obviously restrained. That was because advantageous surface environmental conditions offset resistance of the cyclonic vortices, which made them lasted longer. The intensely developed supercell storm with obvious meso-anticyclone had features as hook echo and inflow notch at the low level, bounded weak echo region (BWER) at the middle-upper level and reflectivity core and strong storm top divergence at the upper level. These echo features were similar to classic cyclonic right-moving supersell except with anticyclone and the echo feature being approximate mirror image of cyclonic supercell storm. Storm splitting began at the initial stage of the formation of cells. The splitting occurred at the middle-upper level at first and then extended downward rapidly. After the division, relative to the 0-6 km wind shear vector, the left cells were anticyclonic left-moving storms and the right ones were cyclonic right-moving storms.