A low-pressure system over the Bay of Bengal is likely to intensify into a cyclone by early next week, the Met office said on Friday.
It will be the Bay’s first cyclone of the year. Once it intensifies, the cyclone will be named Arnab, meaning ocean or sea, a name given by Bangladesh.
The system is likely to move towards the north Andhra Pradesh and south Odisha coasts, according to a Met bulletin issued on Friday. It is too early to predict the exact location or timing of landfall, officials said.
South Bengal is likely to receive rain between October 27 and 30, with heavy showers possible in coastal districts. Calcutta is forecast to receive moderate rainfall for now.
System status
On Friday morning, the system was a low-pressure area over the east-central Bay, the Met bulletin said. “A low-pressure area formed over the east-central and adjoining southeast Bay of Bengal around 5.30am on October 23. It persisted over the same region at 8.30am. The associated cyclonic circulation extends up to 5.8km above mean sea level.”
The system was about 1,000km from the Bengal coast in a straight line.
Projected path
The system is likely to intensify into a depression by Saturday and a deep depression by Sunday before developing into Cyclone Arnab by Monday, according to the forecast.
“It would then continue to intensify further and move west-northwestwards towards north Andhra Pradesh and adjoining south Odisha coast during the two subsequent days,” the bulletin said.
Favourable conditions
Cyclones feed on heat and humidity. The sea surface temperature in the region is around 29° Celsius. Sea temperature above 26° is considered favourable for cyclone development, Met officials said.
“The absence of strong wind shear is also important. The last strong system over the Bay had intensified into a depression but weakened because of strong vertical wind shear, which is not unusual during the monsoon,” said H.R. Biswas, head of the forecasting section at the Regional Meteorological Centre in Alipore.
A similar low-pressure system developed over the Bay in the third week of September, when monsoon currents were still active. It intensified into a deep depression but could not strengthen further because of wind shear, Biswas said.
The system made landfall in Andhra Pradesh as a deep depression on September 23. As it moved towards Chhattisgarh and Odisha, it triggered heavy rain in Calcutta.
Rain forecast
Squally winds are likely along and off the Bengal coast from October 27, while heavy rain is very likely in some districts till October 30, the bulletin said.
South 24-Parganas, East Midnapore, Bankura and Jhargram are among the districts likely to receive heavy rain between October 28and 30.
“More specific forecasts about the landfall area and the likely track of the storm will follow. As of now, there is a strong probability that the system will turn into a cyclone and head towards the Andhra-Odisha coastline,” a Met official said.
South Bengal, including Calcutta, is likely to remain dry until the system approaches the coast. “After that, the humidity will rise,” the official said.