Multiscale Characteristics Of Tornadoes In Suzhou And Wuhan On May 14,2021

On the night of May 14,2021,the tornado process appeared in Suzhou and Wuhan one after another.Based on the combined reflectivity puzzle products of Shanghai Qingpu Station SAD dual polarization radar,Wuhan SA Doppler radar,the new generation weather radar network,the multi-source high-resolution observation data of the ground minute by minute encryption automatic weather station and ERA5 reanalysis data,the weather background,ground trigger mechanism,radar detection characteristics and environmental parameters of this process are compared and analyzed,and the WRF model was used to conduct large eddy numerical simulation of the tornado process in the two regions,exploring the mutual configuration between different environmental conditions before and during the tornado occurrence.The main conclusions obtained are as follows:(1)Suzhou and Wuhan tornadoes both 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 ultralow level jets.Among them,the western side of the Suzhou tornado occurrence is located in the strong convergence zone of the eastern jet exit area,The location of the tornado in Wuhan corresponds to the exit area of the western jet stream,which is conducive to generating strong boundary layer low level vertical wind shear.The Suzhou tornado has a ground convergence line formed by the convergence of multiple supercell storm outflows and warm air flows from the East China Sea.It moves from west to east and affects the tornado activity area.The convergence line interacts with multiple supercell.When the convergence intensity increases,it promotes the development of the parent storm.The Wuhan tornado has a mesoscale convergence center on the ground,which is weaker than the mesoscale trigger condition of the Suzhou tornado.(2)Both tornadoes were generated from isolated rightward moving supercell.When the lower Mesocyclone suddenly strengthened,the tornado vortex characteristics(TVS)were detected 2 min and 3 min before the tornado,respectively.In addition,the tornado fragment characteristics(TDS)could also be detected in Suzhou tornado.The supercell that produced the Suzhou tornado lasted for a long time,with a life history of two hours.The supercell that produced the Wuhan tornado quickly generated,developed,produced the tornado,and then quickly disappeared,with a life history of about 40 minutes.(3)Suzhou tornado has strong convective effective potential energy,low uplift condensation height and convective suppression energy,and moderate and weak storm relative helicity and vertical wind shear conditions.Wuhan tornado has weak convective effective potential energy,low uplift condensation height,high convective suppression energy,and strong storm relative helicity and vertical wind shear conditions.Both the convective storm activity area and the vicinity of the tornado occurrence area show that the thermal conditions of the Suzhou tornado are good,while the dynamic conditions are moderate to weak;The dynamic conditions of Wuhan tornadoes are good,but the dynamic conditions are weak.The two tornadoes occurred in the form of complementary thermodynamic parameters.(4)Based on WRF model large eddy simulation,the evolution of Suzhou tornado parent storm and tornado like vortex are reproduced.When there are low uplift condensation height and convective suppression energy,high relative helicity of the storm and vertical wind shear conditions at different altitudes near the supercell storm,and the location of the large environmental parameter corresponds to the inflow environmental wind with high wind speed,tornadoes are likely to occur,The comprehensive index of tornado generation conditions is consistent with the time and location of tornado occurrence.