The Radar Signature of Fatal Convective Wind Events in Spring over South China

Using severe wind reports (more than 25 ms^-1) and Weather Surveillance Radar Doppler data ,this research illustrates the storm morphological characteristics of all 36 fatal straight-line convective winds events of South China in Spring from 2007 to 2014 .The main radar-based morphological storm types include unorganized cellular,quasi-organized cellular (either a cluster of cells or a broken line of cells), organized cellular (supercells and supercells embedded in an organized linear system), and organized linear (either squall lines or bow echoes). It is found that three-fourths of the convective severe wind reports are identified as being produced by organized convective structures rather than by isolated thunderstorm. The occurrence of organized linear types are typically dominant in Spring over South China . The results from base velocity analyses indicate that the appearance of the mid-altitude radial convergence in organized storm types is larger than in the quasi-organized cellular type in which the rear inflow jets occupy the dominant field. The main velocity features of the organized linear storms are the mid-altitude radial convergence (42.9% of the total) and rear inflow jets (47.6% of the total); The strength of the mid-altitude radial convergence for organized linear storms is between 26 and 51 ms^-1, and the depth is thick. According to the ratio of severe precipitation and fatal wind in the same storm, when the position of the strongest mid-altitude convergence layer is lower (less than 4km), the proportion of severe precipitation appears to be large, and the position of the strongest shear of the mesocyclone is also low. The intensity of the inflow jets in organized linear storms is between 20 and 45 ms^-1, which is stronger than that of the quasi-organized cellular storms. It is rare to be observed the corresponding velocity features in advance for the unorganized cellular storm, but the velocity of low elevation angle is large at the moment of occurrence.