A numerical study of the effect of island terrain on tropical cyclones.

Abstract

A triply nested, movable mesh model was used to study the behavior of tropical cyclones encountering island mountain ranges. Realistic distributions of island topography at 1/6o resolution were inserted into the model domain for the region of the Caribbean. It was found that the islands affected the basic flow as well as the wind field directly associated with the storm system. The combination of these effects caused changes in the tract and translational speed of the storm. In particular, in the case of the 5m s-1 E flow, the storm accelerated and veered to the N well before reaching Taiwan. The intensity changes of the storm near and over the islands were strongly related to the latent energy supply and the vertical coherence of the storm system. Advection of dry air from near or above the mountain tops into the storm area caused significant weakening of all the storms moving with the weaker E flow. Storms leaving Hispaniola and moving over open sea quickly reintensified as their vertical structure remained coherent. On the other hand, storms leaving Luzon were disorganized and did not reintensify until several hours later when the vertical coherence of the systems was reestablished.-from Authors