The low formed in the Bay of Bengal and the adjacent Andaman Sea turned into a depression on Sunday noon and could turn into a cyclone, which was named Yaas, on Monday (today).
It could transform into a deep depression at midnight and a cyclone on Monday, said meteorologists.
The cyclone is very likely to hit Bangladesh and Indian coasts during the supermoon. The full moon in May will be closest to the earth in 2021 and the moon will appear bigger, brighter, and redder in some places.
This is the supermoon, which will grace the sky on Wednesday. Scientists believe Yaas will make landfall on 26 May.
Abdul Mannan, a meteorologist of the Bangladesh Meteorological Department, said, "Ocean tides become bigger during the supermoon compared to other times of the year. If a cyclone hits the coast during the supermoon, it comes with an extra risk as it can inundate coastal areas by its high tides."
He said high tides due to the supermoon and tides due to the cyclone together would increase the height of tides.
"Yaas is not moving horizontally till now. It is rotating with a wind speed of 40-50km per hour. This speed needs to reach 62km per hour to become a cyclone," he said.
"As it is moving westward, our risk of being hit by it has reduced a bit. It can move north-westward from its centre. The Khulna coast of Bangladesh and India's West Bengal and Odisha may witness its front face during landfall," he explained.
The BMD advised all seaports of the country to hoist distant cautionary signal number one.
All fishing boats and trawlers over the north Bay and deep sea were advised to come close to coasts and proceed with caution. They were also advised not to venture into the deep sea.
According to BMD, at 12 o'clock on Sunday, Yaas was about 700km south-southwest to Chattogram port, 625km south-southwest to Cox's Bazar port, 710km south to Mongla port, and 655km south to Payra port.
Water resources ministry opens control room
To observe, monitor, and take necessary steps during the cyclone, the water resources ministry opened a control room on Sunday. People were requested to call 01318234560 for any emergency.
The ministry also held a meeting presided by Kabir Bin Anwar, senior secretary to the ministry, while State Minister Zahid Faruk and Deputy Minister AKM Enamul Haque Shamim gave officials the necessary directions.
"Keep the whole manpower ready to take immediate action if Yaas damages any dam. All officials have to stay at the station until the cyclone is over," Enamul told officials.
Preparations in Khulna, Chattogram
Preparations were taken in Khulna and Chattogram to face the cyclone. In Khulna, some 1,048 shelters and 116 medical teams were kept ready.
The Khulna district administration took the initiative to keep the possible damage from the storm to a minimum level and prevent losses of lives and property.
Set up across nine upazilas of the district, 324 of them are permanent shelters and 724 are temporary, including schools, colleges, and madrasas.
Khulna District Relief and Rehabilitation Officer Azizul Haque Joardar said a meeting of the district disaster management committee had been held.
"All members of the committee, non-governmental organisations, cyclone preparedness programmes, the fire service, and other agencies were instructed to prepare," he said.
In Chattogram, the district administration prepared 511 cyclone shelters.
"We have sufficient stocks of food and medicine," said Omar Faruque, executive magistrate of Chattogram district administration.
He said all volunteers and non-governmental organisations had been instructed to be ready for emergency response.
Rain may start from Tuesday
The BMD said there was no chance of countrywide rainfall on Monday (today) and it would rain only in a few places.
"But If Yaas turns into a cyclone and heads northwest, the whole country may see rainfall from Tuesday," said Mannan.
At 9am on Sunday, the BMD in its 24-hour forecast said rain and thundershowers accompanied by temporary gusty and squally wind was likely to occur in a few places of Barishal and Chattogram divisions and one or two places of Khulna, Dhaka, and Sylhet divisions. The weather may remain mainly dry with a temporary partly cloudy sky elsewhere in the country.
Mannan said rain forecasts would depend on how Yaas would react. "We need to observe."