An Idealized Study of QLCS-Supercell Mergers in High-Shear, Low-CAPE Environments

On 22 March 2022, the Propagation, Evolution, and Rotation of Linear Storms (PERiLS) field campaign sampled a high-shear, low-CAPE (HSLC) environment conducive of both a tornadic quasi-linear convective system (QLCS) and pre-line supercells. Surface in-situ instruments were positioned under various research radar dual-Doppler lobes and observed the evolution of 31 pre-line supercells, their merging process with the QLCS, and the subsequent evolution into QLCS mesovortices downstream. Tornadogenesis was achieved with only some pre-merger supercells and post-merger mesovortices, but no statistically significant differences in cold pool properties were identified between tornadic and nontornadic mergers. However, a disruption of the QLCS cold pool strength was evident within 15 minutes of the merger, which then restrengthened farther downstream. These results motivate the investigation into why some mergers prove to be tornadic while others do not.

The goals of this study are to (1) examine in-situ measurements of mergers during the PERiLS campaign and (2) compare these observations to idealized CM1 simulations of HSLC QLCS and supercell interactions. These mergers typically favor the development of low-level vertical vorticity for both the pre-line supercell and the post-merger mesovortex, but the processes that form, enhance and sustain this low-level rotation throughout the QLCS-supercell merger are still not well understood. This presentation will identify how horizontally generated vorticity sources, rapid destabilization ahead of the QLCS, and favorable storm interactions can lead to tornadogenesis at different stages of the merging process from the perspective of both the supercell and the QLCS.