Comparative analysis of environmental conditions and radar characteristics for two tornadoes occurred in Suzhou and Wuhan in 2021

Abstract

Based on datasets from Shanghai Qingpu dual-polarized radar, Wuhan Doppler weather radar, new generation weather radar network mosaic, ground encrypted automatic weather station, and ERA5 reanalysis, a comparative analysis was conducted on the severe tornado weather processes that occurred in Suzhou and Wuhan on the night of 14 May 2021 from the aspects of weather background, ground triggering mechanism, radar detection characteristics, and environmental parameters. Results are as follows. (1) Both tornadoes in Suzhou and Wuhan occurred under the forced background of southwest warm and humid airflow, with low temperature and high humidity in the lower layer being affected by low-level and ultra-low-level jet streams. However, the location of the tornado in each of the two places was different from the corresponding jet stream location. The western side of the Suzhou tornado corresponded to the exit area of the eastern jet stream, while the Wuhan tornado corresponded to the exit area of the western jet stream. (2) The Suzhou tornado was triggered by the convergence line caused by gust fronts and a weak cold pool with appropriate intensity. Nevertheless, there was a mesoscale convergence center and a weak cold pool on the ground. (3) Tornadoes in both places occurred when the isolated rightward-moving supercells were accompanied by a suddenly strengthened low-level mesocyclone. And tornadic vortex signature (TVS) appeared 2 min and 3 min before the Suzhou tornado and Wuhan tornado, respectively. (4) Different from the environmental conditions of tornadoes occurring in the United States, the Suzhou tornado appeared under the conditions of high convective available potential energy, low lifting condensation height, convective inhibition energy, and medium to weak storm-relative helicity and vertical wind shear. Wuhan tornado occurred under the conditions of weak convective available potential energy, low lifting condensation height, high convective inhibition energy, and strong storm-relative helicity and vertical wind shear. By comparison, before and during the occurrence of tornadoes in the two regions, the thermal condition of the Suzhou tornado was favorable and the dynamic conditions were standard or even unfavorable. However, for the Wuhan tornado, the thermal condition was relatively weak, while the dynamic conditions were favorable. It is indicated that both tornadoes occurred in environments with complementary thermal and dynamic conditions.

Keywords

• tornado
• ultra-low level jet stream
• ground convergence line
• vertical wind shear
• environmental parameters