Abstract:One supercell triggered severe thunderstorm gales in the Pearl River Delta on 11 April 2019 and another supercell induced an EF3 strong tornado in Xuwen County of Zhanjiang City on 13 April 2019. Based on multi-source observations, the synoptic situation, ambient conditions, structure of the storm,triggering characteristics of convective storm, and formation of the severe thunderstorm gale and tornado in the two events are comparatively analyzed.The results are as follows. The severe thunderstorm gales occurred under the southward shear line in the lower layers and the surface cold front, which was classified as the baroclinic frontogenesis severe convection. The strong tornado was the southerly warm advection forcing sector severe convection. The ambient conditions in both days were characterized by high energy strong 0-6 km vertical wind shear, low lifting condensation height and the stratification of dry in the upper level and wet in the lower level. But the sounding at Qingyuan Station on 11 April shows that 0-1 km vertical wind shear was small and average depression of the dew point was 29.2℃ in middle levels. This condition was favorable for the formation of strong downdraft. However, the sounding at Haikou Station on 13 April shows that strong 0-1 km vertical wind shear was favorable for the tornado. On 11 April, the thunderstorm gales were located at the core of the supercell. The low-level mesocyclone was weaker and had a larger diameter of 6-7 km. The rotation depth of mesocyclone was below 2 km. On 13 April, the tornado occured at the top of the hook echo accompanied by low-level intense mesocyclone with the minimum diameter of 2 km and tornadic vortex signature. The rotation depth mesocyclone was up to 6 km. Vertical vorticity remained unchanged at the order of 10-2 s-1 before and after the thunderstorm gales. However, the tornado occurred during the magnitude of low-level mesocyclone vertical vorticity increased to be 10-1 s-1 rapidly, which was an order of magnitude larger than the vertical vorticity of strong thunderstorm gale event. The strong downdraft of the storm produced a large area of intense cold pool on the ground on 11 April, which was favorable for the formation of thunderstorm gales. The saturated atmosphere on the ground and the less strong downdraft of the storm were conducive to the occurrence of strong tornado.