Workshops > CSCAMM Day 2010

CSCAMM Day 2010

On the Rapid Intensification of Hurricane Wilma (2005)

Da-Lin Zhang

University of Maryland


In this study, a 120-hour cloud-resolving prediction of Hurricane Wilma (2005), covering its initial 18-h spin up, an 18-h rapid deepening and the subsequent weakening period, is performed using the Weather Research Forecast (WRF) model with the finest grid length of 1 km. The model initial and lateral boundary conditions, including its bogus vortex, are taken from the Geophysical Fluid Dynamics Laboratory's then operational forecast data, but with the specified daily sea-surface temperatures from satellite observations.

It is shown that the WRF model prediction compares favorably to the best track analysis, satellite, radar and reconnaissance flight observations as well as the vortex message. In particular, the model reproduces Wilma?s rapid intensity intensification (RI) rate of more than 7 hPa h-1 for a 12-h period, its minimum central pressure of less than 880 hPa, and the subsequent weakening and reintensification in the surface maximum wind. Of significance is that the model captures a sequence of important inner-core structural changes associated with Wilma?s intensity variations, namely, from a partial eyewall open to the west prior to RI to a full eyewall at the onset of RI, rapid eyewall contraction during RI, the formation of double eyewalls at the most intense stage, and the subsequent eyewall replacement leading to the weakening of Wilma, followed by another eyewall replacement cycle near the end of the 120-h prediction. In addition, the model reproduces the polygonal eyewalls, and the boundary-layer growth up to 750 hPa with an intense inversion layer above near the eye center.

Recognizing that a single case does not provide a rigorous test of the model predictability, our results suggest that it is possible to improve the forecasts of hurricane intensity and intensity changes if the inner-core structural changes and storm size could be well predicted using high-resolution cloud-resolving models with realistic initial conditions.

Joint work with Hua Chen.