On the reasons and quantified prevalent ocean atmosphere roles for the intensification and genesis features of the ESCS Tauktae

Abstract

Tauktae was an Extremely Severe Cyclonic Storm (ESCS) that occurred in the Arabian Sea (AS) during 14–19 May 2021. The present study investigates the prevalent role of the ocean/atmosphere on the genesis and intensification of it, and causative ocean-met factors from a climatological and current perspective; and tries to understand the reason of intensification though it was close (~ 140 km) to the coast. In general, the climatological Genesis Potential Index (GPI) is higher off the Indian west coast during the cyclone seasons, in which, low-level absolute vorticity (ABV) and mid-tropospheric relative humidity (RH) have major roles to play. Sea surface temperature (SST), RH, and ABV have shown a rapidly increasing trend in the last decade comparing the previous three decades. Before the genesis of ESCS Tauktae, SST was > 31 °C, tropical cyclone heat potential was > 130 kJ cm−2, and there were higher upper ocean heat content and RH, and reduced vertical wind shear observed. Higher value of GPI (> 70) played a significant role in the intensification of ESCS Tauktae. Ocean played a role of 47%, while that of atmosphere was 53% for the intensification of ESCS Tauktae. The combination of La-Nina and Negative-IOD (Indian Ocean Dipole) shows higher RH, and ABV over the eastern Arabian Sea. Also, a notable MJO (Madden–Julian Oscillation) phase and substantial MJO activity (amplitude > 1) are seen throughout the North Indian Ocean (NIO) in May 2021.