Investigating the longevity of significant-tornado producing supercells

Housenga, Rylan J

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https://hdl.handle.net/2142/115443 Copy

Description

Title

Investigating the longevity of significant-tornado producing supercells

Author(s)

Housenga, Rylan J

Issue Date

2022-04-27

Director of Research (if dissertation) or Advisor (if thesis)

Frame, Jeffrey

Committee Member(s)

• Sriver, Ryan
• Trapp, Robert J.

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)

• supercell
• longevity
• significant tornado

Abstract

All 1,515 significant (EF-2+) tornadoes and their environments between 2008 and 2018 in the United States are examined, with a focus on parent supercell thunderstorm longevity. Almost all significant tornadoes are produced by discrete supercells (66%) or clusters (27%), and they are most common in the Plains or Southeast between March and June, with a small secondary peak in November in the Southeast. Bulk wind shear and storm-relative helicity (SRH) are moderately correlated (r ≈ 0.35) with the total time that a supercell is discrete, the total number of significant tornadoes produced by a storm, and the total tornado path length associated with a storm. There is no correlation between storm longevity and any thermodynamic variable. Long-lived (≥ 4 hours) supercells are most frequent in the Southeast, where shear and SRH are typically greatest. Additionally, SRH is roughly 50-70 m2 s-2 greater for the longer-lived supercells (≥ 75th percentile) than for the shorter-lived ones. Another key finding is that excessive (≥ 90th percentile) backing or veering of the wind shear vector above 1 km above ground level (AGL) is detrimental to supercell longevity.

Graduation Semester

2022-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2022 Rylan Housenga

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