Doppler Radar Observations of Horizontal Shearing Instability in Quasi-Linear Convective Systems

AbstractDual-Doppler radar observations of two cold-season, wave propagating Quasi-Linear Convective Systems (QLCS), which evolved in high-shear, low-CAPE (HSLC) environments, are analyzed to determine the role that Horizontal Shearing Instability (HSI) plays in the formation of mesovortices. One QLCS occurred on 4 Jan 2015 and produced two mesovortices within the dual-Doppler region, one of which was associated with an EF-1 tornado with a path length of 10 km. The second QLCS occurred on 28 Nov 2016 and did not produce any mesovortices. Storm characteristics such as the low-level wind speed and wind shift angle are investigated. Rayleigh and Fjortoft instability criteria, which are required but insufficient for HSI, are also examined. The Rayleigh and Fjortoft instability criteria are satisfied for the 4 Jan 2015 QLCS and the 28 Nov 2016 QLCS, highlighting one of the issues of the ”required, but insufficient” characteristic of the criteria. Analysis of the wind shift angle and wind speed agree with previ...