From noon to night, nerves taut .... Amphan can pack wind speeds above 100kmph in Calcutta

Dark clouds hover over the Hooghly river and the Howrah Bridge on Tuesday afternoon. Picture by Pradip Sanyal

Debraj Mitra, TT, 20.05.20, Calcutta: What looked like a speck over the South Andaman Sea a week ago has snowballed into the second strongest storm in over two decades on the Bay of Bengal and is advancing towards the coasts of Bengal and Bangladesh.

Cyclone Amphan is expected to make landfall between Digha and Hatiya Island (Bangladesh) near the Sunderbans from Wednesday afternoon to evening.

The monstrous cyclone is losing steam as it approaches land but is still tipped to unleash high-speed winds, heavy rainfall and a storm surge that can sink low-lying areas.

The effect of the cyclone is expected to be felt from 12 noon on Wednesday. The edge of the storm is expected to touch land around 2pm and the entire system should pass through by 9pm, said Met officials.

A ship at Haldia Port is bound to the dock by an array of ropes, more than the usual one each at the front and the rear, on Tuesday Sourced by The Telegraph

“Calcutta is expected to see winds blowing at 50kmph since morning. The speed is expected to go up further to 70kmph as the day progresses and reach a peak of 100-110kmph as landfall time comes closer,” said G.K. Das, the director of the India Meteorological Department, Calcutta. The city is also expected to witness heavy rain.

Police and urban local bodies have issued advisories for residents, including keeping parked cars with the handbrake on. (See Metro)

As thick as the clouds hovering over several parts of eastern India was a sense of foreboding at the inopportune invasion by the elements in the middle of the coronavirus pandemic.

“Morar upor khaanrar gha,” chief minister Mamata Banerjee said, describing the approaching storm with an adage that suggests “blows of the sword to a corpse”.

Strength

Amphan is the second strongest storm on the Bay of Bengal since the 1999 Odisha super cyclone, said Mrutyunjaya Mohapatra, a senior scientist and cyclone forecasting specialist at the IMD, New Delhi. Mohapatra has led the tracking efforts that began in the second week of May, focused on what was then a low-pressure zone near the South Andaman Sea.

At one point on Monday night, Amphan had become the only super cyclone after the Odisha one over 20 years ago.

“The 1999 super cyclone had generated sustained wind speeds of 260-280kmph. Amphan had winds blowing at 230-240kmph,” Mohapatra said.

By Tuesday morning, Amphan had depleted from a super cyclone to an extremely severe cyclone.

The strength of storms is determined by wind speeds generated at their peak on the sea. Amphan had touched its peak wind speed on Monday night and the storm would lose some of the steam by the time it makes landfall.

Aila, a severe cyclonic storm that had ravaged the Sunderbans in 2009, had winds blowing at 110kmph during landfall.

Path

The system had been moving north-northwest at the beginning. But it did not travel in a straight path. Around Monday morning, it started to re-curve and travel in a north-northeast direction towards the Bengal and Bangladesh coasts.

A Met bulletin on Tuesday evening said Amphan was an “extremely heavy cyclonic storm over west-central Bay of Bengal about 360km from Paradip (Odisha) and 510km from Digha”.

It is expected to continue its north-northeastward journey and hit land. After landfall, the storm will pass through Bangladesh as a weakened depression, said a Met official.

The system is moving at a speed of 18kmph, said a Met bulletin.

Landfall

“The storm is a huge system that will take close to five-six hours to make a complete landfall,” said Mohapatra. The storm has a diameter of around 700km.

Even the depleted storm is expected to generate wind speeds of over 150kmph during landfall, with gusts clocking 185kmph, the Alipore Met office has said.

The core or the eye of a cyclonic storm is a relatively quiet zone, surrounded by the spiralling bands of winds.

As a storm passes, an area will experience the peripheral winds in the front. As the relatively calm core passes through land, there will be a brief lull. That will be followed by the passage of the rear winds, which are just as strong as the ones at the head of the spiral.

Calcutta connect

The storm is tipped to make landfall between Digha and Hatiya Island near the Sunderbans. Digha is 180km from Calcutta and the Indian Sunderbans around 110km. The peripheral or outer spiralling winds of Amphan are expected to brush the city.

Cradle

What looked like a small dot on an expanse of blue to meteorologists became a 700km-wide storm raging towards land.

“A low-pressure area had been hovering near the South Andaman Sea since April-end but it was becoming less marked every now and then. On May 13, the system became a well-marked low-pressure area and kept becoming stronger,” Mohapatra told The Telegraph.

The low pressure turned into a deep depression over southeast Bay of Bengal. On May 16 evening, it had intensified into a cyclone and further strengthened to a super cyclone on Monday.