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

[AAS03-07] Fine-Scale Radar Observations of Tornado Events Associated With Typhoon Shanshan (2024)

*足立 透¹、益子 渉¹、梅原 章仁¹ (1.気象研究所台風・災害気象研究部)

キーワード：フェーズドアレイレーダー、台風、竜巻

During the approach of Typhoon Shanshan (2024), 12 damaging wind events happened in Tottori, Miyazaki, Saitama, and Gifu prefectures in Japan. Japan Meteorological Agency (JMA) conducted damage surveys of these events and confirmed that at least nine events in Miyazaki and Saitama were caused by tornadoes. Out of them, seven tornado events in Miyazaki were located in the inner/outer rainband 140–275 km northeast of the typhoon center, among the regions with the highest frequency of typical tropical cyclone (TC) tornadoes. On the other hand, the other two events in Saitama were located beyond the outer rainband ~900 km east-northeast from the typhoon center, a region where TC tornadoes are infrequent. Based on the JMA meso/local analysis data, these two tornado events were produced by thunderstorm systems with a structure of miniature supercell that had developed on the northeast side of a small-scale low-pressure system, where the energy helicity index was locally enhanced. We analyzed these untypical TC tornado events using the high spatiotemporal resolution data obtained by phased array weather radar (PAWR), which enables a full-volume scan within a range of 60 km every 30 seconds. We successfully clarified the generation processes of the tornadic vortex: enhanced convection of the storm systems due to their passage over a preformed local convergence line, multiple descending reflectivity cores, increasing rear-flank gust front, and the formation/enhancement of small-scale vortex in the near-surface region around the damaged area. In the presentation, we will summarize the damaging wind events associated with the typhoon and discuss the physical processes of the Saitama tornado events based on the PAWR data analysis.
Acknowledgment: This work is supported by JSPS KAKENHI Grant JP21K03666 and JP24K07143.