Analysis of a rare hail-producing tornado event on 20 March 2013 in Dongguan,Guangdong Province

Based on conventional surface and upper-air data,reanalysis data from NCEP/NCAR,and nonconventional data from Doppler weather radar and surface automatic weather station(AWS),we analyzed a disastrous severe convective weather event with rare tornado and hail on 20 March 2013 in Dongguan,Guangdong Province.The results are summarized as follows.1) The pressure,temperature,wind direction,and wind speed observed at the station passed over by the tornado clearly have different characteristics from those caused by thunderstorm gales.2) The following factors provided a favorable atmospheric condition for the development of convections:the increasing strong wind with altitude in Southern China,the unstable potential stratification with the dry air above and humid air below,and the high humidity and temperature in the low-levels.Additionally,cold air moving southwards,and meso- and micro-scale convergence systems near the ground served as a trigger mechanism for the tornado event.3) The genesis of the tornado is possibly resulted from the moderate convective available potential energy(CAPE),deep and strong vertical wind shear between 0 and 6 km,and 0-1 km low level wind shear.4) The strengthening of convective storms associated with the hail-producing tornado is closely related to the intensifying of the meso- and micro-scale convergence systems near the ground.5) The strongest radar echo is 72 dBz,observed when hail,gale and tornado occurred simultaneously.The tornado occurred near the hook-shaped echo embedded in a supercell close to the rear V-shaped gap.Three body scattering(TBSS) echoes were observed multiple times,which corresponds to hails.The low-level weak echo region,and mid- and high-level echo pendency can be found in radar reflectivity vertical profiles,and the bounded weak echo region(BWER) emerges 20 minutes earlier than tornado.When tornado emerges,tornado vortex(TVS) and mesocyclone in the supercell storm can be found in the radial velocity chart.