Collaborative Research: Supercell Left Flank Boundaries and Coherent Structures--Targeted Observations by Radars and UAS of Supercells Left-flank-Intensive Experiment (TORUS-LItE)

Supercell thunderstorms are responsible for the majority of significant tornadoes in the United States. However, not all supercells form tornadoes and the false alarm rate for tornado warnings is stubbornly high. This small field campaign will use a variety of instrumentation, including radar trucks and uncrewed aerial systems (UAS) to observe atmospheric boundaries that form in what is known as the left flank region of a supercell. The idea is that observing small scale motions and boundaries near supercells will allow us to better understand why some supercells form tornadoes while others do not. Beyond the practical operational forecasting aspect of this project, the field campaign will provide 15-20 students with the opportunity to participate in the collection of data. This award is for the Targeted Observations by Radars and UAS of Supercells Left-flank-Intensive Experiment (TORUS-LItE), an observational study of specific processes in the left flank of supercell thunderstorms and how they relate to tornadogenesis. The research team will deploy UAS, radar, sounding, and mobile Mesonet assets during a three-week period in May and June 2023 in the Great Plains to directly sample boundaries and coherent structures. The investigators believe that advancing understanding of the relationship between supercell tornadogenesis and left/forward flank boundaries and coherent structures requires cross-sectional datasets that enable characterization of the structure and evolution of these boundaries and associated coherent structures in the context of supercell/mesocyclone strength and proximate evolution of near-surface rotation. The science questions to be studied are: A) How often are left/forward-flank boundaries coincident with enhanced vorticity and how does the magnitude of this vorticity relate to the characteristics of the associated boundaries and environmental/ambient state? B) Do the characteristics of streamwise vorticity currents (SVCs) and associated boundaries attendant to tornadic storms differ significantly from those associated with non-tornadic storms? C) Can the dense-side airmasses of left-flank boundaries be characterized as density currents and are SVCs the attendant Kelvin-Helmholtz (KH) billows? This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.