Mesoscale characteristics of a rare severe hailstorm event

Abstract

This study analyzed the environmental field, physical quantify fields, convection parameters and radar echo characteristics of a severe hailstorm that occurred on June 18, 2013, due to a mesoscale convective system. The analysis was performed using ground meteorological data, sounding data and GFS-ANL (gfs 0.5° × 0.5°) reanalysis data in combination with satellite cloud imagery and Doppler radar observations. The results showed that this rare hailstorm event was generated under the influence of a weakening and eastwardly moving low vortex over Lake Balkhash; and a distinct shear line in the middle and lower troposphere over the western South Xinjiang. Strong vertical wind shears, deep conditionally unstable stratification, ample water vapor in the lower troposphere and suitable wet-bulb zero heights are important contributors to the formation of severe hailstorms. An increase in convective available potential energy (CAPE) and a decrease in the lifting index are strong indicators of a severe hailstorm. For the studied hailstorm event, the time corresponding to the maximum value of the normalized CAPE was close to the timing of the actual hailstorm. The severe hailstorm, consisting of multiple supercells, exhibited notable characteristics of hail clouds and supercells. The formation, disappearance and replacement of strong convection cells occurred while the supercells were sustained. The tracking and forecasting results obtained using the Thunderstorm Identification, Tracking, Analysis and Nowcasting system are found to be, to a certain extent, able to indicate of the direction of the supercell storms during this severe hailstorm event.