On the Multiscale Processes Leading to an Extreme Gust Wind Event in East China: Insights From Radar Wind Profiler Mesonet Observations

Abstract

In this study, a record-breaking surface gust wind event of over 45 m s⁻¹, which occurred in the coastal region of East China during the early evening hours of 30 April 2021, is examined. The dynamical characteristics of this event is explored by using a high-resolution mesonet comprised of eight radar wind profilers (RWPs), surface observations, radar and satellite data. Observational analyses show the development of several cloud clusters ahead of the axis of a midlevel trough with pronounced baroclinicity, and the subsequent organization into a comma-shaped squall system with a leading convective line over land and a trailing stratiform region moved offshore. The latter is embedded by a mesovortex with intense northerly rear inflows descending to the surface, accounting for the generation of the gusty winds. Results indicate the different roles of multi-scale processes in accelerating the surface winds to extreme intensity. Specifically, the large-scale baroclinic trough provides intense background rear inflows that are enhanced by the formation of the mesovortex, while moist downdrafts in the rear inflows account for the downward transport of horizontal momentum, leading to the generation of intense cold outflows and gusty winds close to the leading convective line. Despite the lack of sufficient observations for quantitative analysis, this study provides a qualitative analysis that offers valuable insights into the dynamics of extreme gusty winds. Moreover, the above results underscore the value of RWP mesonet observations in enhancing our understanding of extreme wind events and in improving the nowcasting and prediction efforts in the future.