Observations of Misovortices within a Long-Lake-Axis-Parallel Lake-Effect Snowband during the OWLeS Project

Abstract

Recent lake-effect snow field projects in the eastern Great Lakes region have revealed the presence of misovortices with diameters between 40 and 4000 m along cyclonic horizontal shear zones within long-lake-axis-parallel bands. One particular band in which an abundance of misovortices developed occurred on 7 January 2014. The leading hypothesis for lake-effect misovortexgenesis is the release of horizontal shearing instability (HSI). An analysis of three-dimensional dual-Doppler wind syntheses reveals that two criteria for HSI are satisfied along the horizontal shear zone, strongly suggesting that HSI was the likely cause of the misovortices in this case. Furthermore, the general lack of anticyclonic–cyclonic vortex couplets throughout the event reveal that tilting of horizontal vorticity into the vertical is of less importance compared to the release of HSI and subsequent strengthening via vortex stretching. A WRF simulation depicts misovortices along the horizontal shear zone within the simulated band. The simulated vortices display remarkable similarities to the observed vortices in terms of intensity, depth, spacing, and size. The simulated vortices persist over the eastern end of the lake; however, once the vortices move inland, they quickly dissipate. HSI criteria are also calculated from the WRF simulation and are satisfied along the shear zone. Competing hypotheses of misovortexgenesis are presented, with results indicating that the release of HSI is the likely mechanism of vortex formation.

Gap-Filling Mobile Radar Observations of a Snow Squall in the San Luis Valley

“…The radar detected a number of horizontal circulations, including a persistent mesovortex on the end of the squall and a number of misovortices along the gust front. The presence of misovorticies is consistent with studies that reported similar features on thunderstorm gust fronts (e.g., Friedrich et al 2005), and sea/lake-effect snow (e.g., Inoue et al 2011;Steiger et al 2013;Mulholland et al 2017).…”

A Case Study of Anomalous Snowfall with an Alberta Clipper

“…Such cold-season airflow patterns are common around the world, often resulting in the development of significant snowbands in the Great Lakes region of the United States (e.g., Mulholland et al [42]), the Gulf of Finland (e.g., Savijärvi [43]), and the Sea of Japan (e.g., Ueda et al [44]), as well as the English Channel and Irish Sea (e.g., Norris et al [45]). The difference in this case to these other examples is that while the significant snowfall occurred over the lower Great Lakes region of the United States, Lake Erie appeared to be of little consequence in the generation of the localized heavy snowfall amounts.…”

Single- and Dual-Doppler Radar Analysis of Misovortices within Snowband in Japan Sea Coastal Region on 17 January 2017

“…This study showed fine scale aspects of misovortices within the snowband using high 15 resolution single-and dual-Doppler radar observation. The misovortices with ζ~0.03 s -16 1 developed along the shear line with cyclonic shear (~0.006 s -1 ) and convergence 17 (~0.007 s -1 ). It is possible that HSI, rather than HCRs, was the likely cause of the 18 misovortex formation as in the previous studies of misovortices within the snowbands.…”

“…They examined the relationship between misocyclone intensity and environmental 22 characteristics and concluded that misocyclone intensity was found to be more closely 23 horizontal shearing instability (HSI) is the likely mechanism of vortex formation 14 (Mulholland et al 2017). Although specifics of the evolution of larger mesoscale vortices 15 (~ 4-100 km diameter) in snow events have been documented (e.g., Kawashima and 16…”