Radar-Based Characteristics of Tornadic and Nontornadic QLCS Mesovortices during PERiLS

A long-standing forecasting challenge is the low predictability of tornadoes spawned by quasi-linear convective systems (QLCSs). QLCS tornadoes typically form within a parent vortex known as a mesovortex (MV); however, not all MVs are tornadic, which adds to the forecasting challenge. This research uses observations collected during the Propagation, Evolution, and Rotation in Linear Storms (PERiLS) field campaign in the Southeast U.S. to examine radar-based characteristics that could differentiate tornadic (TOR), wind-damaging (WD), and non-damaging (ND) QLCS MVs.

19 QLCS MVs passed through the University of Illinois Flexible Array of Radars and Mesonets (FARM) C-band on Wheels (COW) radar domain during the 2022 PERiLS deployments. MVs have been manually identified and quantified over their entire lifetime using data at the lowest elevation angle of the WSR-88D and the COW radar scans. Results show that although TOR MVs have stronger rotational velocities (Vrots) over their whole lifetime, TOR and WD MVs have similar Vrots when examined before the first report/warning was issued. When analyzing the diameter of MVs before the first report/warning was issued, TOR MVs typically have smaller diameters, which could be helpful from a forecasting perspective. Two QLCS MVs have been observed at the lowest elevation scans in the WSR-88D data but not in the lower altitude-sampled COW data during a part of their lifetimes. This raises the question, can QLCS MVs exist aloft at severe wind intensity and not produce surface damage? This question is further investigated by analyzing the depth of the MVs from radar data, examining data collected from ground-based pods, and conducting a WRF simulation of one of these cases.