April 11, 2022 - 3:30 pm
April 11, 2022 - 4:30 pm
CategoriesConvective Meteorology (Mesoscale Dynamics)
Convective Meteorology (Mesoscale Dynamics)
14 April 2018 Shreveport-Bossier City, Louisiana QLCS Tornadoes: A Study of Tornadic Mesovortices and Their Lifecycles
Monday, April 11
Mesoscale-gamma circulations that occur along the leading edge of mature Quasi-Linear Convective systems (QLCS) have been documented in literature for a number of years. In fact, numerical simulations and a few observational datasets have linked these circulations and QLCS-associated tornadoes. Despite widespread recognition of this relationship, specific details of mesovortex generation, maintenance, and their influence on tornadogenesis remain ambiguous. During the early morning hours of 14 April 2018, a QLCS containing numerous mesovortices tracked through northwest Louisiana, producing several tornadoes. Two noteworthy mesovortices entered the observational domain of the VORTEX-SE field campaign near Shreveport, LA, allowing both University of Oklahoma C-Band, Shared Mobile Atmospheric Research and Teaching Radars (SMART-Rs), and the KSHV WSR-88D the opportunity to sample these features.
The resulting dataset allowed for two separate analysis domains with dual-Doppler coverage to be synthesized, one between SMART-R1 and KSHV, and the other between SMART-R1 and SMART-R2. Employing 3-D variational wind retrievals within these dual-Doppler domains elucidated details of mesovortex processes and vertical structure, particularly at low levels where they were most impactful and influenced the tornadogenesis process. Results suggest that a similar, two-part process occurred in both mesovortices 1-3 minutes before tornado formation, beginning with the vertical tilting of predominantly crosswise horizontal vorticity by a local downdraft in the vicinity of the mesovortex. Shortly thereafter a nearby, rapidly strengthening updraft stretched this vorticity, intensifying the circulation to tornadic levels. Streamwise vorticity was also implicated in the tornadogenesis process, as there was an increase in the magnitude of streamwise vorticity tilting near the mesovortex-associated updraft just prior to a rapid intensification of vertical vorticity. The impact of these processes on the lifecycles of the observed mesovortices is examined, along with a brief overview of potential future research avenues.