Evaluating the CAPE-Shear Parameter Space of Southeastern US QLCS Environments

The Propagation, Evolution, and Rotation in the Linear Storms (PERiLS) field campaign was conducted to sample the environmental and storm-scale processes associated with tornadic quasi-linear convective systems (QLCSs) in the Southeastern United States. QLCS tornadoes present operational forecasting challenges in this region because they are less well-understood than supercellular tornadoes. These tornadoes frequently occur in environments with large low-level vertical wind shear and weak instability (commonly known as “high-shear, low CAPE”, or HSLC, environments). In these HSLC environments, values of CAPE and shear favorable for QLCS tornadoes may only overlap across small sections of the convective line of a QLCS. One way to address the forecasting challenge associated with QLCS tornadoes is to gain more knowledge about the environments associated with tornadic HSLC QLCSs. Specifically, improving the understanding of 1) what section(s) of the CAPE-shear parameter space QLCS tornadoes preferentially form in as well as 2) where favorable values of CAPE and shear tend to overlap in relation to the convective line of the QLCS would potentially aid forecasters in anticipating the location of potential tornadic activity in HSLC QLCSs.

To analyze the CAPE-shear parameter space of HSLC QLCS environments, this study utilizes High Resolution Rapid Refresh (HRRR) model data to analyze the pre-storm environments associated with 100+ cold season (November-May) QLCSs identified from November 2014 – May 2023 using the Storm Prediction Center’s Severe Weather Event Archive and archived National Weather Service Weather Surveillance Doppler Radar (WSR-88D) data. We will document CAPE-shear parameter space of HSLC QLCS environments and analyze the portion(s) of this parameter space in which QLCS tornadoes were documented. Observations collected during the PERiLS field campaign will be used to further analyze the pre-storm environments of 12 QLCSs.