Analysis of a Long-Track Tornadic Supercell Occurring within a Stable Boundary Layer during the VORTEX-SE Field Campaign

On March 19, 2018 during IOP1 of the VORTEX-SE Year 3 field campaign, semi-discrete convection formed in Northeastern Alabama within a variable, albeit uniformly cool, stable boundary layer environment north of a surface warm front. Despite significant cloud coverage and precipitation over the region preventing significant destabilization of the PBL, one cell rapidly intensified into a long-track supercell that propagated along the Northern Alabama border for over 175 km. Although this supercell occurred within an environment typically thought to be non-conducive to tornado production, the storm produces one long-track (62 km) high-end EF2 tornado, followed by one EF1 tornado throughout its lifespan. Other notable characteristics of this supercell include the apparent lack of cold pool within the rear-flank downdraft region and bore-like signatures in close proximity to the supercell, both of which were observed utilizing crowd-sourced meteorological observations.

Given the positioning of various VORTEX-SE assets, including mobile/static Doppler radar, upper air sounding teams, and PBL profiling platforms, in conjunction with the aforementioned crowd-sourced surface observations, a substantial dataset from this unique event was collected. This presentation aims to present a comprehensive analysis of the evolution and lifecycle of this tornado-producing supercell and its spatially-varying mesoscale environment through a synthesis of dual Doppler radar, high-resolution VAD analyses, profiler, radiosonde, and surface observations. Results from the analysis of these extensive observational datasets will then be used to investigate the mechanisms responsible for tornado production within this stable boundary layer, and present preliminary results regarding the possible impacts that stabilizing processes may have had on enhancing the tornadic potential of the storm through modification of the ambient thermodynamic and kinematic variables.