Characterizing the Nature and Evolution of Asymmetric Structures in Idealized Simulations of Rapidly Intensifying Tropical Cyclones

Conceptual models of tropical cyclone (TC) evolution are often established in the context of axial symmetry and deviations from axial symmetry, primarily designated as asymmetries or eddies. Satellite and radar imagery of numerous TCs depict a variety of asymmetric structures during all stages in the TC life cycle, with some of the more salient asymmetric features arising from contrasts in the nature of convection embedded within the TC circulation. A wealth of prior studies has documented bouts of asymmetric convection during the rapid development phase of a TC that aid in moistening the incipient vortex and concentrating potential vorticity (PV) near its core. Proceeding the developmental phase, low-wavenumber PV asymmetries near the TC core persist throughout the rapid intensification phase and are often accompanied by continued bouts of asymmetric convection prior to the TC achieving its maximum intensity. Therefore, we are motivated in this study to explore the nature of asymmetries emerging during TC rapid intensification and to understand their contributions to the structural development and intensification of the symmetric TC circulation. We present a wavenumber-frequency PV spectral analysis to characterize the length and time scales of asymmetries present during the rapid intensification of a TC within an idealized numerical simulation. Transient and persistent PV asymmetries are noted throughout the rapid intensification phase and are found to influence the structure and intensification of the symmetric circulation. An Eularian PV budget along with parcel trajectories will be presented during the beginning, middle, and end of the simulated TC rapid intensification to further elucidate asymmetric contributions to the intensifying symmetric circulation. Preliminary findings indicate the symmetric generation of PV via combined asymmetric sources of heating and vorticity is vital to aiding the development of a hollow PV tower during intensification. This distinct structure is often manifested as a vorticity ring in aircraft observations of intensifying TCs.