Dynamical mechanisms for secondary eyewall formation: insights from a cloud-resolving tropical cyclone model

An idealized, high-resolution, cloud-resolving configuration of the Weather Research and Forecast Model (WRF) is used to model the evolution of secondary eyewall formation and eyewall replacement cycles in hurricanes. Particular emphasis is placed on evaluating existing dynamical frameworks for secondary eyewall formation. Angular momentum and potential vorticity budgets of model output emphasize the importance of the secondary circulation and rainband diabatic heating on the azimuthal mean concentration of angular momentum and potential vorticity, respectively, in the region of secondary eyewall formation. The build up of these quantities outside of the primary eyewall is consistent with an increase in low-level inertial stability in the region of secondary eyewall formation, which provides an increasingly more efficient region for concentric eyewall development. Utilizing WRF model output, a linearized, nonhydrostatic model provides further insight into the importance of inertial stability in the success of secondary eyewall formation.