The Effect of External Forcing on the Structure Change of Tropical Cyclones

A simple approach to the problem of tropical cyclone development is to utilize a numerical model of an isolated axisymmetric vortex contained in a finite domain. In this case, given the surface boundary condition, the forcing working on the model storm is of internal nature, i.e., the diabatic heating and the surface friction. The structure of a resulted vortex is characterized by its vertical coherency, quasi-balanced gradient wind and associated warm core, eye and eyewall.

In the present study, we assume an open domain. This enables us to investigate effects of the vorticity and enthalpy transport by the so-called environmental wind, i.e., external forcing, on the mechanism of structure change of tropical cyclones. The topics we will discuss include 1) the processes of formation of tropical depressions, 2) factors favorable for making a super intense storm and 3) processes of extratropical transition of a tropical cyclone.