The onset of the squall season was announced by a powerful Nor’wester that swept the city on Monday night, felling trees and smashing window panes.
Tuesday was largely dry.
The next couple of days are also likely to follow suit, according to the Met forecast. But another spell of thunderstorm may head Calcutta’s way between March 20 and 22, said a Met official.
“We have reports of
trees either uprooted or partially damaged at around 40 places, most of them in south Calcutta,” said an official of the Kolkata Municipal Corporation.
Areas in Tollygunge, Behala and Alipore were most affected, he said.
On Monday, the Met office issued a thunderstorm alert for Calcutta and some neighbouring districts around 8.45pm.
Soon after 9pm, the winds started picking up speed. Terrifying streaks of lightning lit
up the sky between 9pm and 10pm.
The Met office recorded a maximum wind speed of 72kmph at Alipore around 9.15pm. The Alipore observatory, which is the official record-keeper for Calcutta, got around 17mm of rain between Monday night and Tuesday night, almost all of it between 9pm and 12.30am.
“The rain-bearing thunderclouds started taking shape over the Jharkhand-Bengal border. The clouds then kept moving, causing thunderstorms in several districts,” the Met official said.
Jhargram, Bankura, Howrah and West Midnapore were some of the districts lashed by formidable rain and powerful winds, he said.
Hailstorms were reported from some parts of Howrah, Jhargram and the southern fringes of Calcutta. “Monday’s storm was the first Nor’wester of the season,” said the official.
A squall is a storm that usually brings rain. A Nor’wester is a squall that originates
over the heated Chhotanagpur Plateau in the late afternoon and sweeps through parts of eastern India over the next three to five hours at a wind speed of over 45kmph. It is usually followed by a brief spell of rain.
The thunderclouds that reached Calcutta were around 15km tall, powerful enough to unleash fierce winds. The wind speed recorded at Alipore was the maximum, said Met officials.
Sunday was also consistently breezy in Calcutta, but there was hardly any rain. That changed on Monday.
The storm dragged the mercury down sharply. At 30.6° Celsius, the maximum temperature was almost four degrees below what is normal for late March. The minimum, recorded just before sunrise, was 18.4°C, five degrees colder than normal.
“The chances of another thunderstorm are low until Friday. Between Tuesday
and Friday, the mercury will rise. But the heat accumulated near the surface of the earth will be an ally to the moisture when the time comes for another spell of thunderstorm,” said a Met official.