Evidence for the role of barotropic processes in the rear flank downdraft in tornadogenesis

Numerous historical data sets, as well as data obtained during VORTEX, confirm that the supercell rear-flank downdraft draws down quasi-horizontal vortex lines from aloft. In this largely barotropic process, the cyclonic upward-extending lines are concentrated by stretching in the low-level updraft, leading to the formation of the tornado cyclone. The upward-extending anticyclonic member infrequently also is intensified, producing anticyclonic tornadoes which accompany their cyclonic counterparts.