Analysis of radar echo features and environmental backgrounds of a rare severe convective weather in Shandong province

Based on Doppler weather radar data, conventional observation data and regional automatic station meteorological data, the severe convective weather event causing severe hail and thunderstorm in Shandong Province on August 16, 2019 is analyzed. The results are as follows. (1) The strong convective weather event is triggered by the surface meso -β convergence line and meso -γ vortex under the background of northeast cold vortex. (2) The typical characteristics of thunderstorm and hail are large vertical temperature lapse rate in middle and low layer, inversion layer near surface, the dry and cold at top and warm and wet the bottom vertical stratification, and the suitable 0℃ and -20 ℃ wet bulb temperature layers'height. (3) The convective cells triggered by the meso -β convergence line developed and merged, forming squall lines with loose arrangement among them, while some cells near the meso -γ vortex developed into a supercell storm. (4) The super cell storm with strong hail in Zhucheng has the characteristics of bounded weak echo area, three body scattering, side lobe echo and mesocyclone. The characteristics of severe thunderstorms include the rapid weakening after reaching its peak, the rapid decline of strong center height, the emergence of strong reflectivity factor area in the left rear of storm low level, the strengthening of cyclonic rotation intensity in the right front side of the low level of storm, the deep and lasting mesocyclone, and the strong vertical shear of wind.