Simulation of pre-monsoon cyclones of two contrasting monsoon years using mesoscale model WRF (ARW)

Abstract

Tropical cyclones are known for their devastation in tropical regions over the whole globe. The devastation is mainly due to high winds, intense rains and the associated storm surge. The life cycle of a tropical cyclone is dependent on a number of environmental factors (Gray, 1968) which are frequently present in the Inter Tropical Convergence Zone (ITCZ). These include a warm ocean surface (above 26° C) and several physical parameters contributing to a deep humid and unstable atmosphere. It is a well established fact that SST 26.6 C is a prerequisite for tropical cyclone formation in the Bay of Bengal. The formation process begins in an area of low pressure coinciding with vigorous convective cloud in the tropics between 5° and 22° latitude. Usually the cloud cluster drifts slowly towards the west as the convection increases and winds begin spiralling in towards the centre of the system. There are two cyclonic seasons in the North Indian Ocean (NIO), pre-monsoon (April and May) and post-monsoon (October and November). Tropical cyclones form in the NIO during pre-monsoon season of which most of these cyclones develop in the Bay of Bengal and hit the Bangladesh or Myanmar coast. Cyclonic disturbances that develop during this season have a high probability of reaching a severe cyclonic stage (Singh et al., 2000).