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Fine-scale Phased-array Radar Observations of an EF2 Tornadic Supercell near Mountain Lee.

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Title: Fine-scale Phased-array Radar Observations of an EF2 Tornadic Supercell near Mountain Lee.
Authors: Li, Zhaoming1 (AUTHOR), Bai, Lanqiang1 (AUTHOR) bailanqiang@foxmail.com, Chan, Pak Wai2 (AUTHOR), Fu, Peiling3 (AUTHOR)
Source: Advances in Atmospheric Sciences. Jul2025, Vol. 42 Issue 7, p1365-1375. 11p.
Subject Terms: *Radar meteorology, *Vortex tubes, *Vertical drafts (Meteorology), *Lead time (Supply chain management), *Radar, *Tornadoes
Abstract (English): This study presents finely resolved radar signatures of multiple cyclonic vortices associated with an EF2 tornadic supercell that occurred in Guangzhou on 16 June 2022 and discusses how the mesocyclone formed on the lee side of mountain. A nearby X-band phased-array radar provides evidence that the mesocyclone was shallow, with a depth generally confined to less than 3 km. The mesocyclonic feature was observed to initiate from near-ground level, driven by the interaction between intensifying cold pool surges and shallow lee-side ambient flows. It was first recognized shortly after the presence of near-ground cyclonic convergence signatures over the leading edges of cold pool outflows. Over the subsequent 17 min, the mesocyclone developed upward, reaching a maximum height of 3 km, and produced a tornado 8 min later. Nearly coinciding with the time of tornadogenesis, a noticeable separation of the low-level tornado cyclone from the midlevel mesocyclone was observed. This shift in the vertically oriented vortex tube was likely caused by modifications to the low-level flow due to the complex hilly terrain or by occlusions associated with rear-flank downdrafts. After tornadogenesis, high-resolution X-PAR observations revealed that the lowest-level mesocyclonic signature contracted into a gate-to-gate tornadic vortex signature (TVS) at the tip of hook echoes. Compared to conventional S-band operational weather radars, rapid-scan X-PAR observations indicate that a core diameter threshold of 1.5–2 km could be employed to identify a cyclonically sheared radial velocity couplet as a TVS, potentially extending the lead time for Doppler-based tornado warnings. [ABSTRACT FROM AUTHOR]
Abstract (Chinese): 摘 要: 针对 2022 年 6 月 16 日在广州生成的 EF2 级强龙卷风, 本研究揭示了其母体超级单体中多个气旋式涡旋的雷达精细观测特征, 并探讨了中气旋在山地背风侧的形成过程。 基于邻近的一部X波段相控阵天气雷达观测, 该超级单体中气旋起源于近地层, 其垂直结构在后续发展过程中主要位于 3 千米高度以下。 在中气旋形成的初始阶段, 雷暴的地面冷池出流不断增强, 并与逐渐增强的山地背风侧浅薄环境气流发生相互作用, 促进近地层气旋式辐合在冷池出流前沿生成。 在该气旋式辐合特征形成后不久, 低层中气旋便被相控阵雷达清晰地识别出来。 在随后的17分钟内, 中气旋向上发展, 最高高度达到 3 千米, 8 分钟后龙卷风触地 (即中气旋形成约 25 分钟后生成龙卷风)。 在龙卷风生成的同时, 相控阵雷达探测到低层龙卷涡旋与中层中气旋发生错位并分离。 这种垂直方向上涡管的空间偏移, 可能是由于低层环境气流在复杂丘陵地形处发生快速转变, 或与后侧下沉气流相关的锢囚过程过程所致。 在龙卷风生成后, 与 S 波段雷达观测特征类似, X 波段相控阵雷达最底层仰角的龙卷涡旋特征 (TVS) 亦表现为格点对格点的 "粘连" 速度对特征。 通过对本次龙卷风案例的综合分析发现, 为充分利用 X 波段相控阵天气雷达的快速扫描和高分辨率采样优势, 若采用 1.5–2 千米的核区直径阈值将低层中气旋判定为 TVS, 将有望获得比S波段雷达更长的龙卷预警时间提前量。 [ABSTRACT FROM AUTHOR]
Database: Energy & Power Source
Description
Abstract:This study presents finely resolved radar signatures of multiple cyclonic vortices associated with an EF2 tornadic supercell that occurred in Guangzhou on 16 June 2022 and discusses how the mesocyclone formed on the lee side of mountain. A nearby X-band phased-array radar provides evidence that the mesocyclone was shallow, with a depth generally confined to less than 3 km. The mesocyclonic feature was observed to initiate from near-ground level, driven by the interaction between intensifying cold pool surges and shallow lee-side ambient flows. It was first recognized shortly after the presence of near-ground cyclonic convergence signatures over the leading edges of cold pool outflows. Over the subsequent 17 min, the mesocyclone developed upward, reaching a maximum height of 3 km, and produced a tornado 8 min later. Nearly coinciding with the time of tornadogenesis, a noticeable separation of the low-level tornado cyclone from the midlevel mesocyclone was observed. This shift in the vertically oriented vortex tube was likely caused by modifications to the low-level flow due to the complex hilly terrain or by occlusions associated with rear-flank downdrafts. After tornadogenesis, high-resolution X-PAR observations revealed that the lowest-level mesocyclonic signature contracted into a gate-to-gate tornadic vortex signature (TVS) at the tip of hook echoes. Compared to conventional S-band operational weather radars, rapid-scan X-PAR observations indicate that a core diameter threshold of 1.5–2 km could be employed to identify a cyclonically sheared radial velocity couplet as a TVS, potentially extending the lead time for Doppler-based tornado warnings. [ABSTRACT FROM AUTHOR]
ISSN:02561530
DOI:10.1007/s00376-024-4094-x