Boundary Layer Processes during Eyewall Replacement Cycle of Hurricane Wilma (2005)

High-resolution numerical simulations have been conducted using the Coupled Ocean/Atmosphere Mesoscale Prediction System – Tropical Cyclone (COAMPS-TC) to understand the role of the boundary layer during the rapid intensification (RI), secondary eyewall formation (SEF), and eyewall replacement cycle (ERC) processes of Hurricane Wilma (2005). The nested-domain simulation of Wilma at the highest grid resolution of 1.67 km captures the RI process as the simulated storm intensified 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 successfully captured hurricane Wilma's SEF, which followed a well-documented path for an extremely strong storm. A new eyewall formed outside of the primary eyewall and propagated inward, and replaced the old inner eyewall during the 24- to 36-h forecast. Detailed diagnostics are performed to investigate the role that the boundary layer (BL) and axisymmetric dynamics played during the RI, SEF and ERC processes. Results show that unbalanced BL inflow plays a critical role during RI. As the primary eyewall intensifies, the associated secondary circulation rapidly decelerates the inflow in BL and initiates convection outside the eyewall. A new eyewall thus forms and contracts, eventually replacing the primary eyewall. Detailed diagnostics and further results will be presented.