Contrast between two severe convections in east Yunnan-Guizhou Plateau

Guizhou Province experienced large-scale severe convective weather on March 16^th to 17^th of both 2022 and 2023, accompanied by hail, strong winds, and short-term heavy precipitation in the two processes. Based on multiple sources of data, the characteristics of circulation, atmospheric environment, radar echo, and cloud image evolution of these two large-scale severe convective weather events were analyzed. The results showed that both the severe convective weather events were caused by the intrusion of strong dry and cold air from 500 hPa during the eastward movement of the upper trough, triggered by the ground convergence line. In both the processes, the outflow of cold pools moved from northwest to southeast, which made the convection develop eastward; the main hail area was near the ground convergence line at the front of the cold pool, and the front end of the cold pool movement was the main area where thunderstorm winds occurred. The SHR6 of the two processes was greater than 20 m/s, the WBZ was at 3−4 km, the −20 ℃ layer was at 6−7 km, the CAPE after correction was more than 1 500 J/kg, the whole layer was an “inverted trumpet” atmospheric junction distribution with dry top and wet bottom, and the atmospheric junctions of both the processes were unstable. The indicators that can be used for the forecast and early warning of hail falling areas are the regions with large relative humidity changes of 700 hPa and 850 hPa and the overlapping regions with large changes of ΔT_700-500 and ΔT_850-500. The hail larger than 20 mm in the two processes were generated by isolated convection cells, and all had echo overhang, bounded weak echo or weak echo, and strong echo centroid larger than 50 dBz.