The Role of Horizontal Shearing Instability in Mesovortexgenesis in the 04 January 2015 Quasi-Linear Convective System (270)

Dustin Conrad, University of Alabama-Huntsville, Huntsville, AL

Kevin Knupp, University of Alabama-Huntsville

 

Abstract:

On 04 January 2015, a quasi-linear convective system (QLCS) traversed across northern Alabama and produced EF-1 damage associated with a mesovortex. The mesovortex formed along a sharp wind shift along the leading edge of the QLCS in a high shear-low CAPE (HSLC) environment. Another mesovortex without associated damage formed further to the south. Doppler and 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). 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. A dual-Doppler synthesis was performed to obtain 2-D winds and vertical vorticity. 2-D wind fields will be analyzed to observe changes in storm scale features such as changes in the sharpness of the wind shift and speed of the flow behind and ahead of the QLCS. Rayleigh and Fj&oslashrtoft stability criteria will be utilized in assessing if HSI is present along the leading edge of the QLCS. Polarimetric data before and at mesovortexgenesis will be discussed as potential indicators of mesovortexgenesis, specifically ZDR columns.