Internal vs. External Forcings in Supercell Interactions and Their Impact on Storm Morphology and Intensity
Syrowski, Ann
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https://hdl.handle.net/2142/31118
Description
Title
Internal vs. External Forcings in Supercell Interactions and Their Impact on Storm Morphology and Intensity
Author(s)
Syrowski, Ann
Issue Date
2012-05-22T00:29:13Z
Director of Research (if dissertation) or Advisor (if thesis)
Wilhelmson, Robert B.
Department of Study
Atmospheric Sciences
Discipline
Atmospheric Sciences
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Supercells
Mergers
Interactions
Tornadoes
Abstract
This study examines supercell interactions from a suite of fifty-two idealized numerical simulations. The relative positions of two storm cells are varied for each case, and a single-cell simulation serves as the control. Despite initializing each simulation with an identical convective available potential energy and wind shear profile, small changes in the initial cell pair orientation lead to significant changes in subsequent storm morphology. Ninety-eight percent of the two-cell storm simulations produce stronger low-level mesocyclones than the single-cell control case, and low-level mesocyclone intensification is coupled with unsteady downdraft bursts in the forward flank. Downburst-driven, surface-based circulation centers form along the forward flank gust front, propagate toward the main updraft, and are stretched immediately prior to mesocyclogenesis events. These discrete rotation centers are approximately one kilometer deep and would most often be unobserved by operational radar. The external forcing associated with the initial storm cell pair orientation modulates the frequencies of the internal downbursts that drive the intensification of the low-level mesocyclone.
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