The Monday evening shower caught many shoppers at Esplanade by surprise. (Sanjoy Ghosh)
Calcutta sweated through Monday afternoon and bathed in a storm in the evening.
The mercury climbed almost two degrees Celsius overnight to reach 34.2 degrees and remained high throughout the day, heating up the moisture in the air and thereby forming a funnel of tall rain-bearing clouds.
The blue sky turned grey around 5.30pm and it started pouring 15 minutes later. North Calcutta received around 12mm to 14mm of rainfall but the southern parts recorded an aggregate of just about 2 to 3mm.
“Many parts of south Bengal, barring Calcutta, were drenched by rain on Saturday and Sunday. The moisture that had accumulated because of a combination of two low-pressure zones in the region remained in the air. The presence of this moisture-laden air in the city created an ideal situation for tall clouds,” said Gokul Chandra Debnath, the director of the India Meteorological Department, Calcutta.
Solar radiation heated up the air since the mercury remained in the mid-30s right from 11.30am to 5.30pm. “So the air began to rise and as it gained height, it cooled down. The moisture condensed to form the cloud. At this point, latent heat was released providing the energy for the movement of air within the cloud,” a weather scientist said.
This explains the gusty breeze that blew for about 15 minutes, between 5.55pm and 6.10pm, when it rained the hardest.
The shower lasted barely half an hour but caught many unprepared for the pre-monsoon smart rain. “I read the rain forecast in the morning but forgot the umbrella. I got drenched while crossing the road to a shade at the Esplanade bus terminus,” said Saikat Maiti at New Market.
“I was walking to Esplanade Metro station when I got caught in the strong wind and rain,” said Soumi Dasgupta, a Lake Town resident.
Cars crawled at the Dorina crossing at Esplanade as traffic personnel let streams of pedestrians cross the wide boulevard to the safety of shades. The wind shook trees around Shahid Minar and blew away tarpaulin shades from the venue of Rahul Gandhi’s Tuesday rally there.
The storm would not qualify as a Nor’wester because it did not blow from the Chhotanagpur Plateau.
But a severe squall swept through the districts, killing two persons in Burdwan. Mahesh Ghosh, 14, was killed by lightning while Rupali Bibi, a 45-year-old homemaker, died when a lamp post fell on her.
For Tuesday, the Met office ruled out any storm but the sky could remain cloudy.