Sequential occurrence and development of three tropical cyclones in the Bay of Bengal in 2013

The Bay of Bengal (BoB) region experienced three sequentially strong tropical cyclones named Helen, Lehar, and Madi during the month of November-December 2013. These cyclones passed over the same region and Lehar formed immediately after Helen dissipated, while the Madi began eight days after Lehar made landfall. The genesis, progression, and subsequent occurrences of these cyclones are investigated in this work. Higher SST is typically a fundamental cause of the development and strengthening of cyclones. The simultaneous occurrence of a weak El-Nino/ Southern Oscillation (ENSO) and the positive episodes of the Indian Ocean Dipole (IOD) raised Sea Surface Temperature (SST) and made it easier for these sequential tropical cyclones to occur. Additionally, at this time, the Madden Julian Oscillation (MJO) Phases 3 and 4 were propagating across the Indian Ocean and Maritime Continent, which supported cyclogenesis by enhancing convective activity that kept the cyclogenesis region with lower vertical wind shear and higher mid-tropospheric humidity. Higher values of tropical cyclone heat potential helped the devel-opment and transformation to higher category stages for both Helen and Lehar cyclones. The values of SST remain above the critical value despite the passage of the above two cyclones, which become ideal conditions for the sequential development of cyclone Madi which was trig-gered by strong MJO activity. The strong high-pressure system on the Indian Landmass is one of the factors responsible for the track reversal of the Madi cyclone.

Automated summary

The Bay of Bengal experienced three strong tropical cyclones in November-December 2013, named Helen, Lehar, and Madi. These cyclones passed over the same region, with Lehar forming immediately after Helen dissipated and Madi occurring eight days after Lehar made landfall. This study investigates the genesis, progression, and subsequent occurrences of these cyclones. Higher SST, weak El-Nino/Southern Oscillation (ENSO), positive episodes of the Indian Ocean Dipole (IOD), and strong MJO activity were found to be the factors contributing to the sequential development of these cyclones.