THE SHELL STRUCTURE OF THE VISIBLE TORNADO VORTEX.
SAINT LOUIS UNIV MO
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The tornado is the smallest yet most destructive of all storms. Its small size, intensity, and infrequency reduce considerably the opportunity to obtain useful data on the region inside of the visible funnel. The closest approach to a recording instrument in reports studied by the writer was three hundred meters. The lack of information regarding the funnel region has seriously handicapped the understanding of the tornado structure. In this study, a first approximate model was developed, principally geometrically and kinematically, to demonstrate the reasonable existence of the shell structure observed in the initial developing stages of tornadoes and waterspouts. This feature was shown to result from a narrow radial zone of subcondensation pressure bounded at the inner radius by contact with dry air in the core of the funnel. Relating the parameters to observations from nature, it was developed that only low level flow of an initial depth of about sixty meters or less should be considered as contributing to the total inflow from the outer region. It was further shown that the radial distance from which a tornado draws its external support is small, about one-half mile or less.