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Figure 4.62. Idealized illustration of how a supercell may behave as it crosses a cold pool (from
Markowski et al., 1998a).
4.10 ROTATING DOWNDRAFTS IN CONVECTIVE STORMS
Strong vorticity is sometimes observed in downbursts/microbursts and the vortex
signature detected by Doppler radar, especially when vorticity is cyclonic, may be
mistaken in an ordinary convective storm for a mesocyclone in a supercell. Failure
to recognize that the mesocyclone is really a rotating downdraft can lead to
inaccurate tornado warnings.
Dave Parsons and Morris Weisman at NCAR demonstrated numerically how
in an environment where vertical shear is too weak to support supercells, a strong,
cyclonically rotating downdraft can be produced when the vertical shear vector at
mid-levels veers with height (the hodograph turns in a clockwise direction with
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