WIND SPEED AND AIR FLOW PATTERNS IN THE DALLAS TORNADO OF APRIL 2, 1957

WALTER H. HOECKER JR. U.S. Weather Bureau, Washington, D.C.

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Abstract

A composite distribution of tangential and upward components of air flow is determined by tracing particles of debris and cloud tag movements in scaled movies of a tornado. The greatest tangential speed measured is 170 m.p.h. and the greatest upward speed derived is 150 m.p.h. A distribution of the convergent radial component of motion in the lower 600 ft. of the vortex is synthesized and used t o generate a vertical speed distribution which nearly duplicates the observed vertical speed distribution.

The observed radial distribution of the vertical component of relative vorticity at three levels is shown and convergence at the 500-ft. radius is computed using the synthesized radial speed distribution. Three-dimensional trajectories of air parcels in the lower portion of the vortex are also shown.

Abstract

A composite distribution of tangential and upward components of air flow is determined by tracing particles of debris and cloud tag movements in scaled movies of a tornado. The greatest tangential speed measured is 170 m.p.h. and the greatest upward speed derived is 150 m.p.h. A distribution of the convergent radial component of motion in the lower 600 ft. of the vortex is synthesized and used t o generate a vertical speed distribution which nearly duplicates the observed vertical speed distribution.

The observed radial distribution of the vertical component of relative vorticity at three levels is shown and convergence at the 500-ft. radius is computed using the synthesized radial speed distribution. Three-dimensional trajectories of air parcels in the lower portion of the vortex are also shown.

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