Radar-Retrieved Three-Dimensional Wind Analysis of Rare Hail-Producing Convection over the Pearl River Estuary

Hailstorms are uncommon over southern China but can cause severe damages during their occurrences. This paper analyzes three recent hail events over the Pearl River Estuary associated with different types of thunderstorm cells, namely, a supercell, a squall line, and a rapidly developing deep-layered single cell. The analysis is based on three-dimensional (3-D) wind fields retrieved from a network of five Doppler weather radars over the region using the Pythonic Direct Data Assimilation algorithm. The three cases took place under rather different synoptic and shear environments but were all favorable for severe updrafts that supported hail development. Retrieved peak updrafts exceeded 30 m/s in the supercell case and reached approximately 18 m/s in the single-cell case. The mechanisms of hail maintenance and deposition in these systems are clearly depicted through 3-D structural analysis of the thunderstorms, essentially the wind field, for their development in multiple time steps. For the first time, the 3-D wind field is also compared with observations from a satellite-borne radar, showing consistent evidence of intense updrafts and convective development reaching approximately 15 km above sea level; isolated hail was observed to descend along the downdraft flank of the cell. The evolution the 3-D structure of these convective systems, in particular the vertical velocity field, provides valuable information for nowcasting of the development of hailstorms.