Dual Doppler Radar Analysis of a Tornadic Quasi-linear Convective System on 04 January 2015

On 04 January 2015, a tornadic quasi-linear convective system (QLCS) impacted northern Alabama where an EF-1 tornado impacted the town of Albertville, located atop the Sand Mountain plateau in northeast Alabama. The tornado formed along a sharp wind shift along the leading edge of the QLCS in a high shear-low CAPE (HSLC) environment. Another non-tornadic mesovortex formed further to the south of the tornado. Doppler and dual-polarimetric radar data were collected from the University of Alabama-Huntsville's Advanced Radar for Meteorological and Observational Research (ARMOR) and the National Weather Service weather surveillance radar 1988-Doppler (WSR-88D) at Hytop, Alabama (KHTX). These data were complimented by meteorological surface observations and data from a 915-MHz wind profiler located at the University of Alabama in Huntsville’s Severe Weather Institute - Radar and Lightning Laboratories (UAH-SWIRLL), and surface data from the Gadsden, Alabama Automated Weather Observing System (KGAD AWOS). It is suspected that the main formation mechanism for the observed mesovortices in this event is horizontal shear instability (HSI) due to the extremely low CAPE and high low-level shear in the environment. Rayleigh, Fjørtoft stability criteria, and horizontal Richardson Number will be utilized in assessing if HSI is present along the leading edge of the QLCS. A possible wave interaction will also be investigated as the cause of the tornadic circulation becoming more intense than the southern vortex. These vortices will also be categorized by size, strength, and depth.