On the upper ocean response of Bay of Bengal to very severe cyclones Phailin and Hudhud

ABSTRACT The upper ocean response of Bay of Bengal to two extremely severe post-monsoon tropical cyclones, Phailin and Hudhud, which occurred in the same time of the season (4–12 October 2013 and 6–12 October 2014 respectively) with very similar tracks and life cycles are presented in this study. It is observed that, even though the tropical cyclone Phailin was much stronger than tropical cyclone Hudhud, the cooling of the underlying ocean was more rapid and intense during the passage of tropical cyclone Hudhud. Heat budget analysis of the upper ocean based on realistic simulations using Regional Ocean Modeling System suggests that, while the vertical processes, horizontal advection and the reduction in the net heat flux have contributed to the cooling of the upper ocean in both the cases, the intensity of vertical processes were relatively weaker in the case of tropical cyclone Phailin. Further analysis shows that the surface layers of Bay of Bengal were relatively more stable in October 2013 due to excess rainfall in the preceding summer monsoon compared to October 2014, which was succeeded by a poor monsoon.