[A-AS03] Extreme Events and Mesoscale Weather: Observations and Modeling

[AAS03-P17] Hectometer-scale forecast of a severe thunderstorm event over Beijing using RMAPS-ST model

*Qianqian Huang¹、Hongjun Liu¹、Yizhou Zhang¹、Xiangyu Huang¹、Xiujuan Zhao¹ (1.Institute of Urban Meteorology, CMA)

キーワード：thunderstorm, gust, RMAPS-ST, hectometer-scale forecast

Thunderstorm, resulting from vigorous convective activity, is one of the most spectacular weather phenomena in the atmosphere. Severe thunderstorms, often accompanied by thunder, squall lines, lightning, and hail, can result in significant agricultural losses, structural damage, and loss of life. On May 30, 2024, between 12:00 PM and 6:00 PM, a convective system traversed the Beijing-Tianjin-Hebei region from west to east, generating extensive thunderstorm winds. The observations showed that 832 meteorological stations experienced winds exceeding Force 8 during the event. 100 stations reached Force 10 and remarkably, two stations even registered winds as strong as Force 13. The linear convection propagated eastward at speeds reaching up to 70 kilometers per hour. The strong winds caused widespread damage, including uprooting numerous trees and power poles. During this event, the vertical wind shear between 0–6 km was weak, and dynamic conditions were unfavorable. The total precipitable water (TPW) across the entire layer was low, contributing to adverse moisture conditions for convective development. While there was potential thermal instability, it contributed to significant uncertainty in convection initiating. In fact, the wind intensity was far stronger than the typical 7–8 Beaufort scale strength for dry convective thunderstorm winds. Among China's regional forecast models, only RMAPS-ST successfully predicted this severe thunderstorm wind event. However, it exhibited limitations by delaying the initiation time and underestimating the movement of convective system. Furthermore, the model failed to forecast the linear convective structure after the convection downslope flows into Beijing urban area. Based on RMAPS-ST's 3 km-resolution forecasts, we refined our forecast resolution to 1 km for the Beijing-Tianjin-Hebei region and further enhanced it to 333 meters specifically in Beijing. The results demonstrate that forecasts at the hundred-meter scale were much better both in depiction of the timing of convection initiation and the linear convective structure. Based on this result, we conducted an in-depth analysis of the complete lifecycle of this unusual thunderstorm wind event.