The city was pounded by one of the heaviest rain spells this season between Thursday night and Friday afternoon as a Bay system, fuelled by active monsoon currents, entered south Bengal and moved towards Jharkhand.
Except for brief intervals, it rained almost non-stop from 10pm on Thursday until 4pm on Friday. The rain spells continued late into Friday.
Conditions are expected to improve from Saturday afternoon as the system moves further away towards Jharkhand, said a Met official. Sunday will likely see sunny intervals. But another wet spell is expected mid-next week, he added.
Most Calcuttans went to bed while it was raining and woke up to more rain. Office-goers and schoolchildren faced a difficult time waiting for public transport. Between 8.30pm on Thursday and 8.30pm on Friday, the Met office recorded around 120mm of rain in Alipore. The civic body’s pumping stations indicated several parts of Calcutta received even more rainfall.
A low-pressure area over the Bay of Bengal on Thursday intensified into a depression by 5.30am on Friday. The depression over the northwest Bay crossed Bengal and adjoining Bangladesh coasts between 7.30am and 8.30am on Friday, said the official.
A Met bulletin said the system was 80km east of Sagar Island and 100km south-southeast of Calcutta around 8.30am after landfall. By 11.30am, the depression remained over coastal Bengal — 50km northeast of Sagar Island and 60km south of Calcutta — moving at 18kmph, said a 4pm bulletin.
It is very likely to move west-northwest across Gangetic Bengal and adjoining North Odisha and Jharkhand during the next 24 hours, it said.
By 5.30pm, the system maintained its intensity as a depression but was 30km from Midnapore town, around 100km from Calcutta, and 130km east of Jamshedpur in Jharkhand, moving at 22kmph.
“Usually, friction from buildings, poles and trees weakens a system after landfall. In this case, the depression faces challenges but continuous moisture from the Bay and land is helping it sustain strength. It will eventually weaken into a low-pressure, but the question is when,” said H. R. Biswas, head of the weather section at the Regional Meteorological Centre in Alipore.
Light to moderate rainfall with streaks of lightning is expected across south Bengal over the next couple of days. Rainfall is likely to rise again from July 28 as the monsoon trough strengthens, said a Met official. A fresh system is also not ruled out. There is a heavy rain alert for Calcutta on July 29.