More squalls have swept through the city since March than in the corresponding period in any of the past four years, keeping the dreaded Calcutta sweat in check and raising hopes of a not-so-uncomfortable summer.
The squall on Monday night, the sixth this season, dragged down Tuesday’s minimum temperature to 22.2 degrees Celsius, five notches less than the previous day’s minimum and three below normal.
There had been only one squall from March 1 to April 21 last year. The result: the minimum temperature exactly a year ago was four degrees above normal at 28.8.
“The frequency of squalls and thundershowers — four in March and two in April — has taken everyone by surprise. They are responsible for the unusually comfortable start to summer this year,” said Gokul Chandra Debnath, the director of the Regional Meteorological Centre at Alipore.
Almost every spell of a steep rise in the mercury was followed by a squall and thundershowers, which reined in the temperature over the next few days.
Officials at the India Meteorological Department (IMD) in Delhi said the city had not experienced more than three squalls between March 1 and April 21 in the previous few years.
“Technically, this is the most pleasant start to Calcutta summer in five years, with the temperatures mostly remaining normal or just below. It could well be the coolest summer this decade if there are another four or five squalls by the end of May,” said an IMD official.
The weatherman attributed the phenomenon to the frequent formation of low-pressure troughs in and around south Bengal and more-than-usual flow of moisture from the Bay of Bengal.
“Together they are aiding the formation of convective clouds over Calcutta and its surrounding areas. Convective clouds trigger squalls and thundershowers during this time of the year,” said Debnath.
In previous years, the low-pressure troughs had been few and far between at the onset of summer.
The conditions resulting in squalls and thundershower could continue for another two to three weeks, said scientists at the Noida-based National Centre for Medium Range Weather Forecasting.
“From what we have seen so far, the situation is unlikely to change before the second half of May. Given the conditions, there could be three more such phases by May 15,” a scientist told Metro over the phone.
If the prediction comes true and the monsoon arrives as usual around June 7, Calcuttans will have to grapple with the oppressive summer heat for just a few weeks.