Assam chief secretary Kumar Sanjay Krishna has asked the Assam State Disaster Management Authority (ASDMA) to be ready with adequate responsive measures to prevent any loss of life because of cyclone Amphan, which is likely to make a landfall over coastal West Bengal on Wednesday afternoon and move to the western districts of Assam.

In a letter to the commissioners of all the four divisions of Assam, chief executive officer (CEO) of the ASDMA and all deputy commissioners, the chief secretary expressed concern over India Meteorological department (IMD) and media reports on strong likelihood of widespread effect of Amphan in Assam.

“You are requested to ensure that both preventive and response systems are put on high alert to avoid any loss of life and property. The SDRF may be kept informed and their help sought whenever necessary,” the letter reads. Krishna has also asked the ASDMA to consider setting up a control room as a responsive measure to minimise the impact of the cyclone.

The IMD, in its report, stated a few districts of western Assam and Meghalaya will witness heavy to very heavy rainfall while most places will get light to moderate rainfall.

The super cyclonic storm will make a landfall over coastal West Bengal on Wednesday. Amphan will cross the Bengal-Bangladesh coast between Digha (West Bengal) and the Hatiya islands (Bangladesh) close to the Sunderbans during afternoon and evening hours of Wednesday with a maximum sustained windspeed of 155-165 kmph gusting to 185 kmph, the IMD stated.

The Nagaland State Disaster Management Authority stated that Nagaland will not be directly impacted by the storm.

Tripura alert: Tripura has alerted all its eight district magistrates as Amphan is likely to move across Bangladesh towards Tripura on Wednesday.

The revenue special secretary S. Choudhury in a letter said: “There is no warning of high impact of Amphan to Tripura but there is no certainty of movement of the exact path of the cyclone as predicted by the IMD. Hence, the administration may be prepared to handle if there are any high impact of this cyclone. The IMD Agartala centre has forecast that there will be thunderstorms accompanied with lightning, the gusty wind speed reaching 40-50 kmph and heavy rainfall at isolated places in the state in all districts on Wednesday and Thursday. I am further directed to request you to be alert and accordingly take necessary preparedness measures at your level to tackle the situation.”

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 supercyclone, said Mrutyunjaya Mohapatra, a senior scientist and cyclone forecasting specialist at 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.

Additional reporting by Tanmoy Chakraborty in Agartala