Date of Award

2017

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Atmospheric Science

Committee Chair

Lawrence D. Carey

Committee Member

Kevin Knupp

Committee Member

Christopher J. Schultz

Subject(s)

Severe storms--Forecasting., Tornadoes., Tornado warning systems.

Abstract

Discriminating if a supercell will become tornadic still remains a difficult forecasting challenge due to similar resemblance in development and structure. This study evaluates rapid decreases in lightning, termed lightning dives, relative to physical processes of kinematic and microphysical properties in identifying supercell tornadic potential and severe weather production. Three supercell cases experiencing tornadogenesis or significant low-level rotation within a dual-Doppler lobe and the North Alabama lightning mapping array were examined from the 2016 Verification of the Origins of Rotation in Tornadoes EXperiment-Southeast (VORTEX-SE) field campaign. The occurrence of a downdraft enhancement generally preceded a triggered lightning dive, with lag times ranging from 10 to 30 minutes after a maximum absolute downdraft of -10 m s-1 or greater. Both nontornadic supercells exhibited the largest absolute magnitudes of rear-flank downdraft velocities and median drop size distributions in the hook echo, possibly due to increased rates of evaporative cooling further enhancing downward motion. Lightning, kinematic, and microphysical characteristics found in these limited sample cases from VORTEX-SE compare well with previous observed research.

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