18C.2 The Role of Vortex Rossby Wave Dynamics on the Early Stage of Concentric Eyewall Formation

Friday, 2 May 2008: 10:30 AM
Palms H (Wyndham Orlando Resort)
Yosvany H. Martinez, Dept. of Atmospheric and Oceanic Sciences, McGill University, Montreal, QC, Canada; and G. Brunet and M. K. Yau


A simple non-divergent barotropic model and the high-resolution Pennsylvania State University-National Center for Atmospheric Research (PSU-NCAR) non-hydrostatic mesoscale version 5 (MM5) are used to study the role of vortex Rossby waves (VRWs) during the early stage of concentric eyewall formation. The Empirical Normal Mode (ENM) and the Eliassen-Palm (EP) flux formulations are applied to the simulated datasets to diagnose vortex Rossby waves processes and their impact on the structure and the primary circulation of the simulated hurricanes. The diagnostic results from the “dry” barotropic case suggest that asymmetric disturbances outside a preexisting annular vortex may relax to form concentric rings of enhanced vorticity that contain secondary wind maxima. On the other hand, the diagnostics of the MM5 full physics experiments showed that the leading ENMs for the wavenumber 1 and 2 disturbances exhibit mainly characteristics of VRWs and their contribution to the EP flux divergence induce regions of secondary mean tangential wind acceleration outside the primary eyewall.

The fact that the critical radius for some of the leading ENMs is closed to the location where the secondary eyewall eventually develops in both the dry barotropic and the full physics experiments implies that a VRW-mean flow interaction mechanism may be suitable to explain important aspects on the dynamics of the formation of secondary eyewalls in very intense hurricanes.

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