Kolkata: A depression in the Bay of Bengal is likely to concentrate into a severe cyclonic storm and make landfall along the adjoining coasts of West Bengal and Bangladesh around May 26 midnight, bringing heavy rain in the coastal districts of the state and in north Odisha, the Met department said on Friday.
This is the first cyclone in the Bay of Bengal this pre-monsoon season and will be named Remal, given by Oman, according to a system of naming cyclones in the north Indian Ocean region.
The system is likely to intensify into a severe cyclonic storm and make landfall between Sagar Island in West Bengal and Khepupara in Bangladesh, the IMD said in a bulletin.
The cyclone could reach a wind speed of 120 kilometres per hour (kmph) on Sunday.
The Met office has warned of extremely heavy rainfall in the coastal districts of West Bengal and north Odisha on May 26-27. Extremely heavy precipitation may hit parts of northeast India on May 27-28.
Storm surge of up to 1.5 metre is expected to inundate low-lying areas of coastal West Bengal and Bangladesh at the time of landfall.
The weather office warned fishermen not to venture into the sea in north Bay of Bengal till May 27 morning.
The Met issued a red alert for West Bengal’s coastal districts of South and North 24 Parganas district on May 26 and 27.
It warned of 100 to 110 km per hour wind speed gusting to 120 kmph in South 24 Parganas and 90 to 100 kmph gusting to 110 kmph in North 24 Parganas on May 26-27, accompanied by extremely heavy rainfall at one or two places on both days.
An orange alert was issued for Kolkata, Howrah, Nadia and Purba Medinipur districts by the Met, warning of 80 to 90 kmph gusting to 100 kmph wind speed, accompanied by heavy to very heavy rain at one or two places on the two days.
The depression, which lies over the central Bay of Bengal, about 660 km south-southeast of Sagar island, is likely to concentrate into a cyclonic storm by May 25 morning, the Met said.
The weather office forecast heavy rain in Purba Medinipur on May 25, on which date elections are scheduled to be held in Tamluk and Kanti Lok Sabha constituencies located within the coastal district.
Moving in a northward direction, the system will further concentrate into a severe cyclonic storm by May 25 evening and cross the coast between Sagar Island and Khepupara around midnight of May 26, the weather office said.
Wind speed will reach 60 to 70 kmph gusting to 80 kmph over Hooghly, Purba Bardhaman and Paschim Medinipur districts, accompanied by heavy rain.
The rest districts in south Bengal will experience wind speed of 40 to 50 kmph gusting to 60 kmph, it said.
In north Odisha, the coastal districts of Balasore, Bhadrak and Kendrapara will receive heavy rain on May 26-27, while precipitation is likely in Mayurbhanj on May 27.
The IMD warned of localised flooding and major damage to vulnerable structures, power and communication lines, kutcha roads, crops and orchards in South and North 24 Parganas districts of West Bengal.
People in the affected areas have been asked to remain indoors and vacate vulnerable structures.
Scientists say cyclonic storms are intensifying rapidly and retaining their potency for longer periods due to warmer sea surface temperatures, a result of oceans absorbing most of the excess heat from greenhouse gas emissions.
The past 30 years have witnessed the highest sea surface temperatures since records started being maintained in 1880.
According to senior IMD scientist D S Pai, warmer sea surface temperatures mean more moisture, which is favourable for the intensification of cyclones.
Madhavan Rajeevan, former secretary of the Union Ministry of Earth Sciences, said a sea surface temperature of 27 degrees Celsius and above is needed for a low-pressure system to intensify into a cyclone.
The sea surface temperature in the Bay of Bengal is around 30 degrees Celsius at present.
“The Bay of Bengal and the Arabian Sea are very warm at present, so a tropical cyclone can easily form,” Rajeevan said.
But tropical cyclones are not only controlled by the ocean but the atmosphere also plays an important role, especially in terms of vertical wind shear — a change in wind speed and/or wind direction with altitude.
“A cyclone will not intensify if the vertical wind shear is very large. It will weaken,” Rajeevan said.
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