Tuesday, 11 January 2000
The Regional Atmospheric Modeling System (RAMS) is used
to examine the formation of a tornado-like vortex within the
simulation of an idealized supercell in a horizontally-homogeneous environment. The vortex achieves a
pressure drop of 20 mb, is 1.5 km in diameter, and is associated with 50 m s-1 winds several hundred meters
above the surface. It does not appear that the vortex forms
by a 'dynamic-pipe' effect; rather, the vortex rapidly
intensifies throughout its depth. However, dynamically-induced pressure perturbations associated with
the modeled supercell do seem to be important for concentrating vorticity at the location of the future
tornado-like vortex. The effect of microphysics on the
evolution of the vortex is also investigated. For example,
when the mean diameter of the hail species is reduced, hydrometeors are advected further away from the concentration point of vorticity. This reduces the eventual
intensity of the tornado-like vortex because the downdraft
associated with these hydrometeors is important to the
concentration of vorticity. The significance of these
model results to the behavior of real tornadic supercells
is discussed.
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