6A.4 Investigating the Effects of Topography on the Generation of Low-Level Vorticity in Simulated Supercells

Tuesday, 23 October 2018: 2:45 PM
Pinnacle C (Stoweflake Mountain Resort )
Branden Katona, Pennsylvania State Univ., Univ. Park, PA; and P. Markowski

Topography is occasionally proposed as a mechanism by which convective environments are modified locally to become more conducive for tornadogenesis to occur in observed supercells. However, it is impossible to know the storm’s potential to undergo tornadogenesis in the absence of topography in a more homogeneous environment. Prior idealized numerical simulations have shown that topography modifies both environmental instability and wind shear, which produce noticeable impacts on both low-level updraft intensity and low-level mesocyclone strength in simulated supercells. A large number of simulations is generated and analyzed to determine how the placement of a bell-shaped hill relative to the supercell track affects the generation of vorticity at the lowest model level. Results will be grouped according to the effects of the terrain on the supercell’s characteristics including vortex generation at the lowest model level, low-level updraft intensity, and updraft helicity. Archetypical runs from each group will be analyzed further in order to learn more about the processes by which terrain can modify storm dynamics to make vorticity generation at low levels more or less favorable. Early results suggest that certain terrain configurations may allow for low-level circulation to be placed more favorably beneath an intense low-level updraft, allowing for increased stretching of vertically oriented vorticity earlier in the simulation when compared to the control run. Additionally, it appears that terrain may baroclinically generate vertical vorticity that is further stretched by the low-level updraft.
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