Simulation of Eyewall Replacement Cycles for Hurricane Wilma (2005)

High-resolution numerical simulations of Hurricane Wilma (2005) have been conducted using the Coupled Ocean/Atmosphere Mesoscale Prediction System – Tropical Cyclone (COAMPS-TC) to understand the rapid intensification (RI), the secondary eyewall formation (SEF) and eyewall replacement cycles (ERCs) processes. The nested-domain simulation of Wilma at the highest grid resolution of 1.67 km captured the RI process as the simulated storm intensifies from Cat-2 to Cat-5 in 24 h, a drop of minimum sea level pressure (MSLP) from 974 hPa to 896 hPa during the 24-h period beginning at 1200 UTC 18 October 2005, which compares well with the best track (minimum pressure falling from 979 hPa to 882 hPa). The model also captured hurricane Wilma's two SEFs and ERCs successfully. The detailed diagnostics of the inner-core eyewall structures have been conducted to examine different mechanisms of formations for SEFs. The first SEF followed a well-documented path for extremely strong storms; a new eyewall formed and propagated inward, and replaced the old inner eyewall. The second SEF occurred during a period when the TC was relatively weak and the new eyewall generated inside the old eyewall. Sensitivity experiments have been designed to improve our understanding of these processes and to assess the roles of planetary boundary layer (PBL) processes and surface conditions. Detailed results will be presented at the conference.