FEEDBACK BETWEEN CONVECTIVE HEATING AND DYNAMICS AND MOVEMENTS OF TROPICAL CYCLONES

It is shown that there exists a mechanism that can cause north-northwe st movement of tropical cyclones in addition to already recognised mec hanisms such as steering current and beta drift. This mechanism depend s on the interaction between organised convection and dynamics. In the initial stages of formation of a cyclone, it is assumed that the hydr odynamic instabilities result in an incipient disturbance that organis es some convection giving rise to a heat source. The atmospheric respo nse to a localized heat source located off the equator in the northern hemisphere produces a low level vorticity field with a maximum in the northwest sector of the original heat source. If the 'Ekman-CISK' whi ch depends on the low level vorticity, was the dominating mechanism fo r moisture convergence, the location of the heat source would move to the new location of vorticity maximum. A repetition of this process wo uld result in a northwest movement of the heat source and hence that o f the cyclone. The movement of a tropical vortex under the influence o f this mechanism which depends on asymmetries created by linear disper sion of Rossby waves is first illustrated using a linear model. It is then demonstrated that this process also enhances the motion of a trop ical vortex in a nonlinear model. Importance of this feedback and the resulting movements of a tropical vortex in determining the actual tra ck of a cyclone and in bogusing an initial Vortex for prediction model s are illustrated.