Increase in the intensity of postmonsoon Bay of Bengal tropical cyclones

The postmonsoon (October-November) tropical cyclone (TC) season in the Bay of Bengal (BoB) has spawned many of the deadliest storms in recorded history. Here it is shown that the intensity of major TCs (wind speed > 49m s-1) in the postmonsoon BoB increased during 1981-2010. It is found that changes in environmental parameters are responsible for the observed increases in TC intensity. Increases in sea surface temperature and upper ocean heat content made the ocean more conducive to TC intensification, while enhanced convective instability made the atmosphere more favorable for the growth of TCs. The largest changes in the atmosphere and ocean occurred in the eastern BoB, where nearly all major TCs form. These changes are part of positive linear trends, suggesting that the intensity of postmonsoon BoB TCs may continue to increase in the future.