On the movement of tropical cyclone LEHAR

Abstract

In this paper, an attempt has been made to delineate the physical processes which lead to the westward movement of the North Indian Ocean tropical cyclone LEHAR. The Advanced Weather Research and Forecasting (ARW) model is used to simulate LEHAR with 27 and 9 km resolutions. In addition to that, all terms of the complete vorticity equation are computed to obtain the contribution of each term for the vorticity tendency. The vorticity tendency is calculated in four sectors, namely northwest, northeast, southwest, and southeast and assumed that the cyclone moves from its existing location to the nearest point where the vortices tendency is maximum. The results indicate that the model performed well in simulating the characteristics of cyclone compared with the Satellite and other observations. It is noticed that the vorticity stretching term contributes most to the positive vorticity tendency. The second highest contribution is from the horizontal advection thus indicating the secondary importance of steering. The distribution of lightning flash rates are higher in the SW and followed by NW sectors of the cyclone indicate more strong convective clouds are in SW sector. The equivalent potential temperatures (θ e) at different stages of before, during and after the mature stage of the cyclone reveals that the wind-induced surface heat (WISH) exchange process is a plausible mechanism for the intensification of LEHAR.