Analysis of the Causes of Torrential Rainfall Event Associated with the Residual Vortex of"Haikui"in Southeastern Guangxi
Utilizing various conventional meteorological data and ERA5 reanalysis data,an analysis was conducted on the causes of the extraordinary torrential rain in the southeastern part of Guangxi in September 2023,induced by the remnant vortex of"Haikui".The results indicate:(1)The South China region was located on the divergent side of the 200 hPa southeastern South Asian High.At 500 hPa,the subtropical high weakened and retreated eastward,while the westerly trough shifted eastward,guiding weak cold air to move southward.This was conducive to the prolonged presence of the"Haikui"remnant vortex over southeastern Guangxi,where the convergence of cold and warm air triggered convection,resulting in extraordinary torrential rain.(2)The low-level monsoon flow strengthened,with convergence of the southwest and southeast winds in southeastern Guangxi.Ample moisture transport to the eastern side of the"Haikui"remnant vortex accumulated,and the favorable alignment of mid-to-upper level divergence with low-level convergence promoted the development of upward motion,providing favorable conditions for the occurrence of extraordinary torrential rain.(3)The backward propagation of convective cells formed a"train effect",with low echo centroids and lifting condensation heights,predominantly characterized by efficient warm cloud precipitation.The ultra-low-level jet stream played a certain indicative role in the emergence of heavy rainfall.
residual vortexextremely heavy rainfallcold airmonsoonwater vapour