Abstract:By reanalysis data (1°×1°) 4 times a day from FNL/NCEP, Doppler radar, and automatic weather station (AWS), this paper analyzed the formation and structure characteristics of the convective storms which resulted in tornadoes from Anhui Tianchang to Jiangsu Gaoyou on 7 July 2013 after analyzing on environmental characteristics and feature extraction of convective parameters of tornadoes in Jiangsu Province in recent ten years’ Meiyu period. The results show that during the Meiyu period in Yangtze Huaihe Region, tornadoes are prone to occur in the right side of mesoscale cyclone (100 km), the lower right side of mesoscale vortex (200-300 km) and the left rear of low level jet stream. General circulation in the Meiyu period provides plentiful moisture, favorable unstable stratification and dynamic conditions for tornadoes. The low level cyclonic vorticity develops strongly before tornado. Vertical wind shear in boundary layer promotes cyclonic vorticity in tornado storm to strengthen rapidly, and enhancement of convergence in low troposphere is conducive to initialization of convection. As for tornadoes in Meiyu period, the demand to convective energy accumulation is lower than hails and thunderstorm gales. Bias between convective parameters feature value and climatic average value provides references for short range forecast of tornado. The tornado convective storm that triggered the tornado on 7 July 2013 initialized near surface convergence line. The strength of surface convergence and mesoscale frontal zone contributed to the development of convective storm. The series of tornadoes were produced by a long life super cell storm which had echo characteristics of typical super cell. The mesocyclone inside the storm maintained two hours. Generally, the evolution of the mesocyclone parameters has great reference value to tornado warning, which shows that when the bottom height is low and shear values are significantly enhanced in the mesocyclone, tornadoes are more likely to occur.