Session 15C.3 On the rapid intensification of hurricane Wilma (2005)

Friday, 14 May 2010: 8:30 AM
Arizona Ballroom 10-12 (JW MArriott Starr Pass Resort)
Hua Chen, University of Maryland, College Park, MD

Presentation PDF (1.4 MB)

In this study, a 72-hour cloud-resolving simulation of Hurricane Wilma (2005) is performed using the Weather Research Forecast (WRF) model with the finest grid length of 1 km. The initial and lateral boundary conditions are taken from the GFDL's then operational forecast data, including its associated bogus vortex in the initial conditions. The sea surface temperature (SST) is updated daily using the observed. This 72-h period covers the initial 18 h spin up, 18-h rapid deepening and the subsequent 36-h weakening period.

It is found that the simulated track is in good agreement with the observed except with a north-westward bias as the model doesn't capture the initial due southward movement in the first 6 h. The model also reproduces the hurricane intensity and intensity changes reasonably well, such as the rapid intensification (RI) rate of 7 hPa/hr for a 12-h period, and the minimum sea-level pressure of less than 880 hPa, and the subsequent weakening in terms of the surface maximum wind.

As verified against various observations, the model captures reasonably well the inner-core structures and evolution of the storm, e.g., the eye, the eyewall, the spiral rainbands and other cloud features. Of particular significance is that the model captures the eyewall structural evolution associated with intensity change. The eyewall evolves from a partial eyewall open to the west prior to the RI to a full eyewall at the onset of RI. During the RI period, the ragged eyewall consolidates and contracts. Around the peak intensity, organized rainbands outside the eyewall start to wrap around and form a second eyewall, leading to the dissipation of inner eyewall. As this eyewall replacement cycle ends, another eyewall forms in the outer region, leading to a new eyewall replacement cycle.

Recognizing that a single case does not provide a rigorous test of the model predictability, the results suggest that it is possible to predict hurricane intensity change associated with the eyewall replacement cycle if high grid resolution, realistic model physics, and proper initial vortex in relation to their larger-scale conditions are incorporated.

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