Plausibility of Substantial Dry Adiabatic Subsidence in a Tornado Core

Abstract

The question of whether or not the cores of some tornadoes are significantly warmed above the moist adiabatic temperature of their parent Cb by dry adiabatic subsidence is discussed in terms of limited supporting evidence and scientific arguments both for and against. Further supporting evidence is provided by axisymmetric numerical simulations described here in which a background field of vertical vorticity is spun up at low levels by a moist convective updraft in a potentially unstable thermal environment typical for tornado events. Substantial axial subsidence heating develops in the simulations provided the vortex swirl is comparable to, or larger than, the maximum values observed in tornadoes. The significant axial forces, including buoyancy, vertical acceleration, and momentum diffusion, are examined in detail for their effect on the surface pressure deficit and the maximum low-level windspeed.