Climate Change

Amphan to make landfall between Bengal and Bangladesh on May 20: IMD

The storm is being said to be ‘unpredictable’ on the lines of Cyclone Fani last year

 
By Akshit Sangomla
Published: Sunday 17 May 2020
Photo: earth.nullschool.net

Cyclone Amphan (pronounced Um-Pun) will make landfall as a very severe cyclone between the Sagar islands of West Bengal and the Hatiya islands of Bangladesh on the evening of May 20, 2020, according to the latest information from India Meteorological Department (IMD). 

The storm formed over south-east Bay of Bengal on the evening of May 16, as had been forecasted by the IMD.

As of now, the storm lies 990 kilometres (km) south of Paradip, Odisha and 1,140 km south-southwest of Digha, West Bengal as a severe cyclone.

IMD predicts that it will move north eastwards initially and then curve towards a north westward direction.

It might intensify into a very severe cyclone by May 17 night and an extremely severe cyclone by the morning of May 19. IMD predicts that the storm will de-intensify a bit before landfall. 

Amphan is the second pre-monsoon cyclone to form in the Bay of Bengal in two years. The pre-monsoon period is generally considered to be unsupportive for the formation of tropical cyclones.

Cyclone Fani had struck Odisha on May 3 last year as an extremely severe cyclone, with wind speeds in excess of 200 km / hour.

Amphan is also touted to have wind speeds of 180 km / hr with gusts of up to 200 km / hr, according to IMD. The points of origin and the tracks of the two cyclones also look eerily similar.

Fani also formed in the south east Bay of Bengal then moved north eastward before turning north westward and maintaining a mostly northward motion towards the West Bengal coast.

After staying on that course for many days, it had made a sudden leftward turn towards the Odisha coast, making landfall after a couple of days.

Fani was an unpredictable cyclone and there have been many such cyclones in the past few years. In October 2018, two very severe cyclones — Titli and Luban — had also behaved unconventionally on either side of the Indian mainland.

Referring to them as the “rarest of rare” occurrences, the IMD had said the movements of both these storms were unique.

While Titli made an unexpected shift in its direction (recurvature) towards the northeast after hitting the coast of Odisha on October 11, Luban made multiple recurvatures for nine days as it travelled through the Arabian Sea before making landfall in Yemen on October 14.

Besides changing tracks, Luban saw rapid intensification and weakening over the sea while Titli saw rapid intensification, which means its wind speed increased by over 55 km per hour within 24 hours.

IMD could not predict it accurately even two days before the cyclone was to hit the coast and missed the landfall point of Titli by 27 km.

A month later, Gaja, a severe cyclone, hit Tamil Nadu with wind speeds of 100-110 km/hr. IMD’s prediction was 80-90 km / hr, which is the speed of a cyclone (63-88 km / hr).

It also made landfall much later than predicted and remained a severe cyclone despite IMD saying that it would de-intensify into a cyclone just before making the landfall.

This is also not a phenomenon being observed only in the Indian Ocean region. Cyclones are becoming increasingly unpredictable worldwide.

In recent years, the United States has witnessed multiple cyclones that gained rapid intensification. In August 2017, Hurricane Harvey strengthened from Category 2 (wind speed 154-177 km / hr) to Category 5 (252 km / hr or higher) in a little more than 24 hours, just before making landfall.

A month later, Hurricane Maria battered the US coast. Its intensification was even more dramatic. It jumped from Category 1 (119-153 km / hr) to Category 5 in 24 hours.

Even during Hurricane Lane in August 2018, scientists could not predict its intensity when it hit Hawaii.

A May 2018 study in the journal Geophysical Research Letters found that the magnitude of rapid intensification events increased from 1986 to 2015 in the central and eastern tropical Atlantic Ocean.

In October 2018, two hurricanes — Willa in Mexico and Michael in the US — witnessed rapid intensification.

“Rapid intensification of tropical cyclones is generally associated with strong warming rate above eye-wall cloud top that extends into the stratosphere, suggesting that stratospheric downdrafts are involved in rapid intensification of tropical cyclones,” a research paper published in the journal Geophysical Research Letters in June 2019, said.

Downdrafts are downward moving air currents originating in the second major layer of the Earth’s atmosphere.

Another December 2019 report prepared by the Geophysical Fluid Dynamics Laboratory of the United States’ National Oceanic and Atmospheric Administration, found that global warming of 2 degree Celsius might increase tropical cyclone intensities by 1-10 per cent for the same size of the storm.

This would mean a similarly-sized storm would carry more destructive potential. There would also be an increase in rainfall brought by the cyclone by 10-15 per cent in a 2-degree warmer world.

The report also said that the possibility of cyclones becoming more intense (very severe and extremely severe category) will also increase due to anthropogenic global warming.

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