Convective evolution during rapid intensification under varying shear

Understanding of the dynamic and microphysical processes resulting in tropical cyclones (TCs) undergoing rapid intensification (RI; wind increase of 30 knots over 24 hours) remains one of the primary research foci within tropical meteorology. RI episodes make up only a small portion of the lifetime of few storms globally each year, however this oft-unanticipated intensification can lead to massive losses of life and property if occurring shortly prior to landfall. Varying modes of rapid intensification dependent upon the magnitude of environmental shear and its impact on the system structure have also been surmised previously in both observational and modeling studies.

To evaluate the dynamical implications of precipitation regimes in RI, two 1-km Weather Research and Forecasting (WRF) model simulations have been undertaken of Hurricane Earl (2010) and Ike (2008). We investigate these cases as prototypes of RI experiencing strong and weak environmental vertical wind shear respectively. The convective system evolution during RI in each of these storms is contrasted in a framework that examines the convective and stratiform rain contributions to vorticity and heating budgets of the cyclone and associated changes in angular momentum preceding and during RI. We also focus on the explicit morphology of convection and its intensity within the TC core, including vortical hot towers and convective bursts as related to the system structural evolution. Discussion of the evolution of each system is related to prior theoretical and observational studies in an attempt to place these simulated case studies within a greater context.