Analysis of the characteristics in a Supercell Storm event in China

Caused by upper level low trough,low level shear and ground cyclone wave, a severe convection with the characters of fast moving, little rainfall was witnessed in Hunan province on April 8, 2008 along with thunder, shower and gust as well as hailstone. Even though no meteorological station but one recorded the trace of this convection with gale, the public and the disaster investigation reported big hail, thunderstorm and gale, which lead great losses such as human life, house collapse and crops damage. This event was caused by a supercell storm. Using the remote sensing data together with the conventional meteorological data, this case was investigated based on meteorological theory, the results show that, from April 6 to 8, Hunan province was controlled by consistent southwest flow, and the low altitude southwest jet provided favorable thermodynamic condition for the convection. The upper air trough lead the ground cold air to go south and formed the cyclone wave in the area of Yangtze and Huai rivers and the meso-scale convective system was triggered in central Hunan province. The diagram of vertical section indicates that, cold and warm advections at different altitudes caused instable vertical structure and the indices such as K, CAPE and SI suggested good condition for storm genesis. The vertical distribution of convergence and energy were favorable for the development of convection and the turbulence at low altitude was the trigger for this event. The auto meteorological stations, lightning detectors and FY-2C geostationary satellite detected the storm with distinct features. The cloud-derived wind of satellite data shows strong divergence at up level of air. The lightning detector indicates high frequency negative lightning during the hail-falling. The Doppler radar suggests the hail storm is right moving with strong reflectivity as high as 65dBz and a top of 12km. There "three-body scattering spider"(Fig.1 and Fig. 2) and side lobe echoes(Fig.3) revealing the hailstones in the severe convection£»The low and mid altitude cyclonic convergence and high altitude gust core in the velocity data are somewhat different from the classic velocity features of severe storm.