Analysis of environmental field and radar echo characteristics for an extreme wind and hail event occurred in Guizhou on 15 May 2021

Based on the routine upper-air and surface observations, the observational data from regional automatic weather stations, satellite images, Doppler weather radar products, we have conducted analysis on the environmental field and radar echo characteristics of an extreme wind and hail event occurred in the northeast of Guizhou on 15 May 2021. The results indicate that (1) this event occurred under the environment of strong warm and humid instability, and it is triggered by the ground mesoscale convergence line at front of cold front. The transport of warm and wet airflow in the south of the shear in the low-level and the strong vertical wind shear are conducive to the continuance and enhancement of convective storm. (2) The great temperature lapse rate and convective available potential energy in the northeast of Guizhou, strong vertical wind shear and low level of free convection (LFC) provide favorable ambient conditions for the hail and thunderstorm gale. When the thunderstorm systems pass, wind speed increases rapidly, air pressure surges and temperature plummets in the weather stations affected by them. (3) The thunderstorm systems gradually form from the original liner multi-cells to the irregularly distributed multi-cell storm systems. The thunderstorm cells show the characteristics by strong echo center with reflectivity factor greater than 60 dBz, high reflectivity factor gradient in south side of the strong echo center and obvious echo overhanging in the mid-and upper-level in the radar reflectivity factor map. The thunderstorm cells that cause downburst are characterized by obvious bow-shaped echo, accompanied by other characteristics such as front inflow gap, rear V-shaped gap and MARC in 4-8 km height. The thunderstorm cells that cause hail are characterized by typical hook echo, accompanied by large VIL value, high echo top height, strong divergence in the top of storm and three-body scattering.