East India coastal current induced eddies and their interaction with tropical storms over Bay of Bengal

Abstract

Eddies of about 10 to 500km in diameter, persisting for periods of days to months are commonly referred to as mesoscale eddies in oceanography. Energetic eddies are frequently found in the vicinity of faster flowing currents like the Gulf Stream and the Kuroshio. The present study deals with the role of eddies, occurring in the vicinity of the East India Coastal Current (EICC), particularly in the months of April to May and October to November, during the intensification of tropical cyclones in the Bay of Bengal. Although the Bay of Bengal is well known for mesoscale eddies, the role of these in the intensification/weakening of the storms is quantitatively unknown. In this study, an attempt has been made to conduct a quantitative analysis of the role of these eddies (warm/cold) in the intensification of the storms over the Bay of Bengal. It is found that in the case of a severe cyclone occurring over the period of 16 to 19 October, 1999 the intensity of the storm was enhanced by 260% due to its interaction with a warm eddy. This is much higher than that reported in case of, for example, Hurricane Opal (119%) and Typhoon Maemi (138%). The enthalpy fluxes (latent plus sensible) are much higher (lower) over warm (cold) eddies. The warm eddy opposes the cooling induced by the storm and helps the intensification through the supply of large amount of enthalpy flux. This emphasizes the importance of eddies in the intensification of storms over the Bay of Bengal, which is omitted by meteorologists in forecasting the intensification of storms.