Using a Three-Dimensional Inertial Frequency to Investigate Vortex-genesis in Supercell Storms

The kinematic nature of the three-dimensional airflow in real-world and simulated storms is largely chaotic but quasi-steady structures develop on specific scales that are characterized by sustained curved flow. A special dynamic interplay between low pressure supplying pressure gradient forcing and inertial acceleration is necessary to maintain flow curvature. While a substantial amount has been learned about the environments in which these structures develop, mechanisms of initiation, rapid intensification and demise are less well understood. A metric is developed from the three-dimensional divergence equation that determines the magnitude of the inertial frequency of the flow from which an absolute curvature voriticity can be estimated. The metric is useful for isolating the part of the flow that develops significant curvature and thus dynamic balance. Although it has a broad range of applications across all scales, the three-dimensionality has provided considerable insight into the generation of a vortex on the tornado scale within numerical supercell simulations. It is shown to be superior for identifying and tracking vortices in highly complex flow fields to many currently employed methods. Following evolution of three-dimensional curved flow in concert with widely used techniques such as lagrangian vorticity budget calculations has shown promise for a deeper understanding of the development, maintenance and decay of intense atmospheric vortices. Examples of its application in understanding supercell tornadogenesis will be presented at the meeting.