24th Conference on Severe Local Storms


Persistent low level mesocyclones in simulated supercell thunderstorms

Leigh Orf, Central Michigan Univ., Mount Pleasant, MI; and G. H. Bryan, R. Rotunno, M. L. Weisman, and H. B. Bluestein

A persistent low-level mesocyclone is widely believed to be a necessary condition for a long-track tornado in a supercell thunderstorm. Proximity studies of environments associated with tornadic and non-tornadic supercells find a strong association between low-level wind shear magnitude and supercell severity, i.e., whether a supercell was non-tornadic, produced weak tornadoes, or produced significant tornadoes.

In this numerical study, the relationship between low-level (0-1 km AGL) environmental wind shear and low-level mesocyclone strength and duration is explored. A series of mesocyclone-resolving numerical simulations is performed across a parameter space spanning weak to strong low level environmental wind shear. Results from these simulations will first be compared to proximity data in order to examine whether the observed relationship between low-level environmental shear and supercell strength is reproduced numerically. Further exploration into the factors contributing towards low-level mesocyclone strength and maintenance in selected simulations will be presented.

Poster Session 10, Numerical Modeling and Weather Prediction Posters
Wednesday, 29 October 2008, 3:00 PM-4:30 PM, Madison Ballroom

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