Application and Applicability of Hydrodynamic Instability Theories to the Formation of Severe Thunderstorms: Free Circulation

Abstract

The feasibility of applying various hydrodyanmic instability theories, previously found applicable in the development of tropical cyclone vortices, to the formative stage of a severe thunderstorm when a meso-low-pressure cell is the dominant circulation feature of the storm's immediate environment is investigated. A consistent grid of meteorological data representative of a meso-low-pressure cell is generated using a model previously described by Lin and Martin. Stability theory of atmospheric vortices is then involved to reflect certain characteristic qualities of an assumed superimposed perturbation upon the generated mesoscale data. The resultant growth-rate equation indicates the determining factors for severe thunderstorm development to be the dimensions of the perturbation and the stability characteristics of the meso-low-pressure cell upon which that perturbation is superimposed. The static stability term representative of the meso-low-pressure cell, in particular, appears to dominate to the extent that perturbations can only grow when an unstably stratified environment exists.