EXPLAINER | Why are cyclones more frequent in India this year?

NEW DELHI: A week after Cyclone Tauktae wreaked havoc in several states, the country is now bracing for second cyclonic storm in the Bay of Bengal and the credit for the cyclogenesis can be given to exceptionally warmer Indian seas this year, making atmospheric and ocean conditions favourable for frequent formation of cyclones and their rapid intensification, says experts.

Threshold value for sea surface temperatures (SSTs) for the formation of cyclones is 28 degree Celsius. At present, SST over Bay of Bengal as well as Arabian Sea is around 31-32 degree Celsius. Rapid intensification is expected to continue to become much more frequent this century with continued climate change. One study found that intensification rates that happen once a century now could happen every 5-10 years by 2100.

Dr Roxy Mathew Koll, Scientist, Indian Institute of Tropical Meteorology, Lead Author, IPCC Oceans and Cryosphere, said: “Similarity between Cyclone Yaas and Tauktae is that both are preceded by very high sea surface temperatures reaching 31-32 degree Celsius. These high temperatures were conducive for cyclone Tauktae to intensify into an extremely severe cyclone in a short time. Similarly, high temperatures are predicted to assist Yaas also for intensifying rapidly.”

He further says that there is one difference. Tauktae spent several days in the Arabian Sea where it could draw the heat and moisture continuously, reaching peak intensity of more than 220 km/hr.

“In the case of Yaas, it has formed in the north Bay of Bengal, and the travel distance to landfall is shorter. As a result, it won't get a long period over the ocean to blow up to the intensity of Tauktae. Here the common thread is that rising ocean temperatures in both the basins are assisting these cyclones in their rapid intensification process. Otherwise, we don’t see a significant increase in the number of cyclones over the Bay of Bengal as we see in the Arabian Sea,” he said.

According to Mahesh Palawat, Meteorologist, Skymet Weather, the credit for the cyclogenesis can be given to climate change.

Indian seas have been exceptionally warmer than usual this year, making atmospheric and ocean conditions favourable for frequent formation of cyclones and their rapid intensification. Rapid intensification is the key point to focus on, as it will have direct impact on rainfall, destruction in terms of floods and gusty winds and evacuation process, added Palawat.

Mahesh Palawat added, “Although the intensity of Cyclone Yaas would be less than that of Tauktae but it would be quite strong in terms of Damage. At the time of landfall, Yaas is likely to give flooding rains along with sustained wind speed of 165-175 kmph gusting upto 185 kmph. Coastal Odisha, Gangetic West Bengal and Jharkhand are expected to be on red alert for widespread torrential rains and damaging winds.”