Multi-Scale Interaction between a Squall Line and a Supercell and Its Impact on the Genesis of the “0612” Gaoyou Tornado

Jiajia Tang,Xiaowen Tang,Fen Xu,Fugui Zhang

doi:10.3390/atmos13020272

Abstract

The interaction between a squall line and a supercell and its impact on the genesis of a tornado that occurred in Gaoyou, Jiangsu Province, China on 12 June 2020 were analyzed using multi-source observations. The tornado formed as the result of an intensified meso-γ supercell in a favorable large-scale environment. The supercell developed in front of a squall line and slowly intensified after its formation. Due to its small size and weak intensity, the supercell did not produce any severe weather before the approaching of the squall line. As the squall line entered its mature stage with the formation of a well-organized bow echo, the supercell in front of the bow echo began to rapidly intensify and finally led to the tornado touchdown. The analysis of mesoscale and storm-scale wind fields indicated that the bow echo of the approaching squall line modified the kinematic fields near the supercell in such a way that was favorable for the intensification of the supercell. The interaction between the squall line and the supercell may have played a critical role in the occurrence of this tornado.

Highlights

Tornadoes are the most violent atmosphere storms which have been recorded on all continents except Antarctica
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The formation of the bow echo and its catching-up with the supercell single doppler radars showed a lower-level mesoscale horizontal shear zone associated with the squall line, which helped to increase the environment vertical vorticity near the supercell

Summary

Introduction

Tornadoes are the most violent atmosphere storms which have been recorded on all continents except Antarctica. According to tornado statistics [14], the majority of non-supercell tornadoes occurred in quasi-linear convective systems (QLCSs), e.g., squall lines and bow echoes. These tornadoes were generally associated with complex interactions between convective systems of different scales. Despite the difficulty of detecting weak tornadoes, the development and interactions of their parent storms may show important precursors for their occurrences [19], providing valuable guidance for operational tornado warning. The environmental condition, structure, and evolution of a squall line and a supercell associated with an EF2 tornado occurred in Gaoyou, Jiangsu Province, China on 12 June 2020 were analyzed.

Wind Retrieval

Evolution of the Squall Line and the Supercell

Discussion and Summary