Comparative Analysis of Environmental Conditions and Structural Features for the Left Moving Supercell and the Supercell in Squall Line in April 2012 Guangdong
In April 2012, a series of severe thunderstorms which produced more hails than normal were seen in the Guangdong Province. This paper analyses two severe convective weather events, which are one left moving supercell in the splitting storm that was observed first time in Guangdong and one supercell in a squall line, by using conventional meteorological observations, Doppler radar data and surface automatic weather station observations. The results show that a “thermal thunderstorm” initiated by local intense heating developed into a supercell storm which produced hails and severe wind gusts on 10 April. On 12 April, one squll line and the supercell which brought hails, severe wind gusts and torrential rains in a very short time were developed by the role of low level warm advection and middle level cold trough in the process of a shear line and a strong cold front moving southeastward, while the vertical wind shears went up by the advection process. The 0℃ layer heights for the two events were lower than the local mean value in April. It was found that the changing of wind shear vector with heights determined the development trend of left moving and righ moving storm: The counterclockwise changing with heights of wind shear vector initiated a left moving storm developed to a hailstorm after storms splitting on 10 April; and the clockwise changing was conducive for a squall line to be well organized and developed, and the supercell in the squall line moved to the right of the mean wind of the bearing layer. The left moving supercell was characterized by a anti mesocyclone, WER, side lobe echoes and a strong echo center on the left side. The supercell in the squall line featured a mesocyclone, WER, side lobe echoes and a strong echo center on the right side, the long TBSS and massive mid level convergence, with 31.1 m·s-1 backside downburst.