Vertical vorticity generation and mesocyclone sustenance in tornadic thunderstorms: the observational evidence.

Abstract

Doppler radar observations concerning the generation of vertical vorticity in tornadic thunderstorms are documented for two case studies and the role of downdrafts in intensifying vertical vorticity is examined. The observations, supporting recent numerical simulations, show that production of vertical vorticity begins at the very roots of updraft as horizontal vorticity in low-level inflow regions is tilted toward the vertical. Then, as the flow passes through the updraft, the tilted vorticity and preexisting vertical vorticity is amplified by convergence to create the tornado parental circulation or mesocyclone. -from Author