Abstract: Based on the conventional observation data, NCEP reanalysis data and Doppler radar data, the mixed severe convective weather on March 20, 2019 in spring （referred to as "March 20"） and August 21, 2019 in summer （referred to as "8·21"） in Hunan province was compared and analyzed. The results show that "3·20" was the warm advection forcing type under the westerly belt system, which brought hail and short-term heavy precipitation, and "8·21" was the quasi barotropic type at the edge of subtropical high, which brought thunderstorm gale. There was no obvious intersection of cold and warm air in "3·20" and no significant deep vertical wind shear in "8·21", which easily led to the neglect of severe convection in the forecast. The two processes had two kinds of sonde curves of upper dry and lower wet type and mixed type respectively, and the difference of stratification characteristics had different indicative significance. Compared with "8·21", "3·20" had better water vapor transport conditions. Both thermal conditions had the characteristics of low warm and humid convection unstable layer and upper dry and cold air intrusion. In terms of radar characteristics, both produced supercell storms, there were characteristic differences such as three body scattering, high hanging strong echo, high radial velocity area, middle-level radial convergence, which indicates that hail or thunderstorm wind was the main. The similarity of mixed strong convection in spring and summer was the focus of prediction work, which played a key role in the forecast and early warning of the main types and falling areas.

Key words: mixed severe convective weather, unstable stratification, three body scatter spike, spring and summer in Hunan