The effects of initial vortex size on tropical cyclogenesis and intensification

Three high-resolution numerical simulations are carried out to investigate the effects of initial vortex size on tropical cyclogenesis and intensification, starting with a relatively weak initial vortex with a maximum tangential wind speed of 5 m s(-1), but located at different radii. In all simulations, there is a progressive organization of convectively induced, cyclonic relative vorticity into a monopole structure. As the initial vortex size is increased, the organization occurs later. In addition, the size of the vorticity monopole, the sizes of the inner and outer core tangential wind circulations and the lifetime intensity of the vortex all become larger. An explanation for this behaviour is offered in terms of a boundary-layer control of the overturning circulation. The findings are consistent with those of previous studies that bypass the genesis stage and start with appreciably stronger initial vortices.