The influences of ENSO on tropical cyclone activity in the Bay of Bengal during October-December

Abstract

The El Niño-Southern Oscillation (ENSO) influence on tropical cyclone (TC) activity (frequency, genesis location, and intensity) in the Bay of Bengal (BoB) during the primary TC peak season (October-December) are studied for the period of 1993-2010. The study shows that during primary TC peak season, accumulated cyclone energy in the BoB is negatively correlated with Niño3.4 sea surface temperature anomaly. Under La Niña regime number of extreme TC cases (wind speed >64 kt) increases significantly in the BoB during the primary TC peak season. The analysis further shows that negative Indian Ocean dipole year is also favorable for extreme TC activity in the BoB during the primary TC peak season. The existence of low-level cyclonic (anticyclonic) vorticity, enhanced (suppressed) convection, and high (low) tropical cyclonic heat potential (TCHP) in the BoB provides favorable (unfavorable) conditions for the TC activity under La Niña (El Niño) regimes together with weak vertical wind shear and high sea surface temperature (SST). The genesis location of TC shifts to the east (west) of 87°E in the BoB during La Niña (El Niño) regime due to the variability in convective activity. The probable reason for the intense TC during a La Niña regime is likely explained in terms of longer track for TCs over warm SST and high TCHP due to eastward shifting of genesis location together with other favorable conditions. The variability of Madden-Julian Oscillation and its influence on TC activity in the BoB during La Niña and El Niño regime are also examined. Copyright © 2012 by the American Geophysical Union.