Calcutta, Sept. 22: After the second highest rainfall in 24 hours in nearly 30 years, the weather office today forecast more of the same for two more days.
“We have issued a warning of heavy to very heavy rain in Gangetic Bengal, including Calcutta, during the next 48 hours,” said G.C. Debnath, director of the weather section at the Regional Meteorological Centre in Alipore.
Poring over their charts and the Doppler satellite image on the computer, weather officials shook their heads in despair as they watched the progress of the low pressure in the north Bay of Bengal as it menacingly intensified.
From Tuesday afternoon, the frown has not left their brows. On Friday morning, the furrows deepened — it had rained 211.6 mm in 24 hours since 8.30 am on Thursday, the highest in the month of September since 1978.
At Tantloi of Birbhum, the rainfall was heavier at 212.8 mm.
“The progress of the system is very slow. When such systems move slowly, it rains incessantly,” said an official.
In the forecast, there was a hint of hope. “Even if the intensity of the downpour lessens in the next 24 hours, the weather will remain inclement for another day,” Debnath said.
Hope may lie also in the formation of a cyclone off the west coast that is likely to move towards Gujarat.Weather officials say the cyclone could draw in moisture from the low-pressure system in the east, lessening its intensity.
Debnath warned: “We are still in the thick of the rainy season and the monsoon is now vigorous over Gangetic Bengal.”
He predicted heavy rain also in some districts of north Bengal in the next 48 hours.
Seeing the possibility, Met officials alerted the state government. “We are in constant dialogue with the relief secretary, Atanu Purakayastha,” an official said.
Explaining the reason for the rain, Debnath said that a low pressure formed below the Bengal delta on Tuesday afternoon and moved slowly towards land, causing squally weather and rain.
This explains the fierce storm in the Sunderbans that claimed 18 lives in the region on Tuesday night.
Then the low-pressure system intensified into a “well-marked” low pressure (the stage before a depression) and hit land on Wednesday covering a large region, including East and West Midnapore and adjoining areas of Purulia and Jharkhand.
As a result, the intensity of the rain increased in the coastal areas and other south Bengal districts. Calcutta received heavy rain as it is near the coast.
“As the system intensified, there was heavy incursion of moisture from the Bay (of Bengal) and the humidity shot up to over 95 per cent and it poured,” said an official.
As Wednesday rolled into Thursday, the low pressure intensified into a depression, bringing even heavier rain.
“The depression on Thursday had its centre close to Jamshedpur. It very slowly inched inside Jharkhand,” said Debnath.
In 24 hours, the depression had move little. On Friday, it lay over Jharkhand with its eye close to Ranchi.
“For the past 24 hours, the depression has been virtually stationary. It is this kind of system that we are scared of. These systems move slowly continuously sucking in moisture and providing the necessary ingredients for incessant rain,” said a Met official.