Comparative analysis of environmental background and radar characteristics of two tornadoes in Huaibei area on 22 July 2020

On 22 July 2020, tornadoes occurred successively in Suzhou, Anhui and Suqian, Lianyungang and Yancheng in Northern Jiangsu. Era-5 (0.25°×0.25°) hourly reanalysis data and radar echo data are used to analyze and compare the weather background, environmental conditions and radar characteristics of the tornadoes. The results indicated that: (1) the two tornadoes occurred under the circulation background of Meiyu period which is conducive to strong convection. Tornado places is located at the edge of the subtropical high. The westerly trough moves eastward on 500 hPa, and the low vortex shear at 700 hPa and 850 hPa is significant. The southwest jet at medium and low altitude is strong and continuously transports water vapor. (2) The similarities of environmental conditions are as follows: strong 0-6 km vertical wind shear and 0-1 km vertical wind shear. The tornado occurred in the high gradient area on the left of the high value center of 0-3 km storm relative helicity S_rh, and near the high value center of energy helicity index E_hi. The ascending motion in front of the Meiyu front is strong and the low-level pseudo equivalent potential temperature θ_se value is large. The difference is only obvious in the Cape value of the two processes. (3) The radar characteristics show that the two tornadoes are caused by the supercell at the south end of the linear convective rain belt, and have obvious mesocyclone characteristics. The hook echo characteristics of the Suzhou tornado are obvious. The northern Jiangsu tornado has obvious inflow gap, bounded weak echo area and suspended echo characteristics.