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Abstract

Increase in the Himalayan glacial melt and associated freshwater discharge during summer through Ganges and Brahmaputra rivers into the Northern Bay of Bengal results in the increased stratification in this region and thereby favoring the intensification cyclones over this region. The cyclone Yaas formed in the Northern Bay of Bengal and moved in the north-easterly direction intensified over high temperatures, and became a Very severe cyclonic storm on 25^th May 2021. The influx of freshwater from the northeastern parts towards the central Bay developed high stratification over this region causing the high heat content top layers and are favorable for the cyclone. The cyclone intensified over a region of warm core eddy which causes further deepening of isotherms by 25-50m due to sinking in addition to the prevailing stratification, which is due to the influx of freshwater from the Brahmaputra river. Along the track, the total incoming short-wave radiation is 420wm^-2 and the long-wave radiation is 430 wm^-2 and the latent heat flux is 200wm^-2. Heat content in the top 30 m varies from 380- 400 wm^-2, which is almost equivalent to the net heat flux. Sufficient energy required for the intensification is available only in the top 30 m water column. As a consequence of high stratification and intense sinking processes, the subsurface nutrient-rich water did not reach the surface. This results in the presence of limited chlorophyll along the cyclone track due to the possible upwelling at the center of the cyclone.