Does Ambient Deep-Tropospheric Vertical Wind Shear Influence Tornado Occurrence during Landfalling Tropical Cyclones?
Landfalling tropical cyclones are capable of producing tornadoes that can compound the damage inflicted by other tropical cyclone hazards (e.g., storm surge) as evidenced by 2017 Hurricanes Harvey and Irma. While current conceptual models suggest that these tornadoes typically occur near the coast to the right of tropical cyclone motion due to coastal processes (e.g., friction gradients), these models do not explain why many tornadoes also occur inland. One unstudied factor that may provide a greater understanding of tornado occurrence during landfalling tropical cyclones is ambient deep-tropospheric (i.e., 850–250-hPa) vertical wind shear, which has been shown to: 1) influence the symmetry and strength of tropical cyclone convection and 2) provide favorable environments for supercells within the downshear quadrants of the tropical cyclone. The present study seeks to examine the role of ambient deep-tropospheric vertical wind shear in influencing tornado occurrence during landfalling tropical cyclones. Results show increasingly stronger ambient vertical wind shear regimes are associated with tornadoes that are increasingly localized to the downshear quadrants of tropical cyclones. This downshear maximum in tornado frequency is associated with favorable dynamic and thermodynamic conditions for supercells in the downshear quadrants likely resulting from the tropical cyclone response to ambient shear.
Bio: Dr. Schenkel is a research scientist in the Cooperative Institute of Mesocale Meteorological Studies (CIMMS) and the School of Meteorology at OU. He holds a B.A. in Environmental Science from Northwestern University and an M.S. and Ph.D. in Meteorology from Florida State University. His present research primarily focuses on the dynamics of the tropical cyclone wind field and its associated hazards during landfall.