Unusually warm Bay of Bengal allowed cyclone Amphan to gain strength
Before the formation of cyclone Amphan, the sea surface temperature in some pockets of the Bay of Bengal in the first two weeks of May was recorded to be as high as 34 degrees C, possibly for the first time ever, scientists from the Indian National Centre for Ocean Information Services (INCOIS), Hyderabad, said.
Even after Amphan passed and its intensity has fizzled out, the temperature in parts of the Bay of Bengal remain as high as 31.5 degrees C, which is above the normal of 28 degrees C for May, and may favour the monsoon, which is near Car Nicobar now.
“I have seen sea surface temperature going up to 32 degrees C earlier but not 34 degrees C. It’s very, very warm and favoured the cyclone in all ways,” said Satheesh Shenoi, director, INCOIS.
The devastation from Amphan may be massive, inundating large stretches of low lying areas, but INCOIS is not able to give figures and data of storm surge or inundation this time because the outbreak of Covid-19 has prevented it from sending a team to the cyclone-affected areas
“Based on details from the ground, we can say that storm surge must have been between 4 to 6 metres in North and South 24 Parganas. We are in a peculiar situation. Usually, immediately after a cyclone, our team rushes to the coast to measure storm surge with our instruments. For inundation, field studies are done to check the mark of water on trees, buildings etc. We can only estimate now that low lying areas of Sunderbans must have been inundated substantially at least for some time because there are narrow bunds and storm surge must have been very high,” added Shenoi.
“This time, Bay of Bengal has been unusually warm. The cyclone was moving only on warm waters which gave it this scale of energy,” Shenoi said.
“Most modelling studies are indicating that category 4 and 5 cyclones are increasing globally while category 1,2 and 3 cyclones are declining. This is something we have to live with as the oceans warm up,” said V Vinoj, climate scientist at the Indian Institute of Technology, Bhubaneshwar.
A study led by School of Earth Sciences, University of Melbourne, last year said that based on projections, tropical cyclone numbers will decrease while their maximum intensities will increase and future sea level rise will exacerbate the impact of storm surge on coastal regions.
“In the past two to three years, we are noticing a rise in tropical cyclones over the Arabian Sea. There are various research papers that are saying that intensity of tropical cyclones has increased but some studies have also contradicted those findings. So I will not be able to comment on that,” said Sunita Devi, in charge of cyclones at IMD.
Last year there were seven severe cyclones (over the Arabian Sea and Bay of Bengal), the first time as high a number was being recorded since 1976, according to data from the India Meteorological Department.