The dynamics of the eyewall evolution in a landfalling typhoon

It has been proposed (Wu et al. 2003) that the terrain plays a unique role in affecting the contraction, breakdown, and regeneration of the eyewall of a tropical cyclone. The recent interaction of Hurricane Wilma with Peninsula Yucatan is a case in point to highlight such an eyewall evolution process. The peculiar eyewall evolution of the landfalling Typhoon Zeb (1998) was studied through a set of numerical experiments using a high resolution meso-scale model (MM5). The major goal of this research is to investigate the effect of terrain, land surface, and ocean on the evolution of the eyewall of a tropical cyclone. Several simulations were conducted with different kind of underlying surfaces. The structures of the eyewall of the simulated tropical cyclones were analyzed. It was found that different underlying surfaces resulted in different eyewall sizes. Potential vorticity mixing of the eyewall and the eye was found when the tropical cyclone made landfall. It was also found that the cutoff of the near core sea surface heat flux can impede the eyewall convection and result in a larger eyewall, while the blocking effect of a mountainous island may bring about an extra large eye. The result from the potential vorticity budget analysis highlights the importance of the mountainous land to the generation of the large eye.