A Three-Dimensional Numerical Model of an Isolated Thunderstorm. Part II: Dynamics of Updraft Splitting and Mesovortex Couplet Evolution

Abstract

Abstract This study analyzes the dynamics of an isolated convective storm embedded within marked ambient vertical wind shear dominated by low-level veering, as simulated by a three-dimensional anelastic numerical modeling experiment. Two particular aspects of the model results, namely, cell splitting and the development of a cyclonic-anticyclonic mesovortex couplet in the updraft, are of main interest. The analysis includes parcel trajectory calculations, decomposition of the pressure perturbation, and examination of the tilting and concentration (stretching) terms as contributors to vorticity generation. It is found that: 1) The updraft is fed by potentially warm low-level air from downshear. This is also the case for the lower part of the main downdraft, which is located upshear of the updraft. Potentially cold middle-level air originating from upshear of the cloud feeds the upper part of the mean downdraft, as well as a secondary downdraft that splits the updraft by propagating inward from the downshea...