Genesis and simultaneous occurrences of the super cyclone Kyarr and extremely severe cyclone Maha in the Arabian Sea in October 2019

• Published in: Natural hazards (Dordrecht) 2022-09, Vol.113 (2), p.1133-1150
• Main Authors: Akhila, R. S., Kuttippurath, J., Rahul, R., Chakraborty, A.
• Format: Article
• Language: English
• Subjects: Civil Engineering; Convective activity; Cyclogenesis; Cyclones; Dipoles; Earth and Environmental Science; Earth Sciences; El Nino; El Nino phenomena; Enthalpy; Environmental Management; Extreme weather; Geophysics/Geodesy; Geotechnical Engineering & Applied Earth Sciences; Heat content; Hydrogeology; Madden-Julian oscillation; Natural Hazards; Oceanic heat content; Oceans; Original Paper; Relative humidity; Sea surface; Vertical wind shear; Wind shear
• ISSN: 0921-030X; 1573-0840
• DOI: 10.1007/s11069-022-05340-9

Arabian Sea (AS) witnessed two very severe cyclones Maha and Kyarr simultaneously in October–November 2019. Here, we analyse the factors that influenced the genesis and simultaneous occurrences of these cyclones. Kyarr (24 October–3 November 2019) is the second super cyclone formed in AS after Gonu in 2007. The path of Maha (30 October–7 November 2019) coincided with that of Kyarr during 1–2 November 2019. The cyclone Maha intensified to an extremely severe cyclone on 4 November 2019, which also encountered a cold core eddy during this period. In general, warmer SST is one of the key factors responsible for the genesis and intensification of cyclones. The co-occurrence of weak El Niño and the positive phase of Indian Ocean Dipole (IOD) during the period increased SST and facilitated the simultaneous occurrence of TCs. In addition, the Madden Julian oscillation Phase 2 and Phase 3 were propagating over the Indian Ocean in this period, which also favoured the cyclogenesis, as these phases lead to enhanced convective activity in maintaining low vertical wind shear and higher mid-tropospheric relative humidity there. Higher oceanic heat content and cyclone heat potential helped the systems to develop and sustain in the higher category stages in the case of Kyarr. The passage of Kyarr cooled SST up to 3.5 °C, but the SST was still higher than 26.5 °C in the region, which provided a suitable environment for the simultaneous occurrence of the cyclone Maha. The positive phase of IOD causes higher than normal SST in AS, which contributes to the cyclone formation, and therefore, five cyclones formed in AS in the same year (2019). Henceforth, this study shows the factors responsible for the formation of simultaneous cyclones in AS and is expected to help the analysis and prediction of such extreme weather events.