An Observational Analysis of the Evolution and Structures of an Extreme Wind Gust Event in East China

This study examines an extreme wind gust event of over 45 m s^-1 occurring in the Yangtze River Delta (YRD) in East China on 30 April 2021, which broke the historical record of surface wind speeds of 221 automated weather stations. A high-resolution mesonet of eight radar wind profilers (RWPs) and six triangular regions along the path of the propagating wind gust is utilized to investigate the dynamics of the extreme wind gust event. Downward transport of turbulence and momentum, and the changes in vertical divergence and vorticity distributions during the event are analyzed. Downward momentum transport likely contributes to the formation of a gust front, and the combination of a gust front and a mesocyclone is of significance in the formation of the extreme wind gust in addition to the large-scale environment. Intensification in mesoscale circulation produced by the merging process likely results in new convection initiation, which potentially accelerates the surface wind through intensified wind shear, and ultimately resulting in the occurrence of the extreme wind gust. This study highlights the role of multiscale processes in the formation of extreme wind gust, as well as the advantage of the non-negligible capability of RWP mesonet in monitoring the turbulence and momentum transport during the passage of the extreme wind systems. The RWP mesonet can serve as a good entry point in extreme wind nowcasting and prediction studies in the future.