The formation of concentric eyewall in hurricane Floyd (1999)

The concentric eyewall is often observed in intense hurricanes. The small inner eyewall could be replaced by an outer one. Such eyewall replacement may result in a rapid change in intensity. It is still not clear how the concentric eyewall forms and how it replaces the inner eyewall.

Hurricane Floyd (1999) was simulated using the high-resolution Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) nonhydrostatic mesoscale model version 5 (MM5). The model successfully captured the formation of the concentric eyewall and the eyewall replacement processes. Our preliminary analyses using the empirical normal modes and the Eliassen-Palm flux suggest that the radially outward propagating vortex Rossby waves coupled with convection contribute to the formation of the secondary eyewall. Detailed results will be presented at the conference.