Two thunderstorms, cloud cover halt mercury climb in its tracks

KOLKATA: Twin thunderstorms hit Kolkata on Friday even as a cloud-mass spread over a 30km radius and 10km in height engulfed the city sky since late morning. The storms, which had a moderate wind speed between 25km/hr and 30km/hr, brought the mercury down by almost 5°C and Kolkata received 8.3mm rain during the day.
While the first thunderstorm struck shortly after 10am, the second one lashed the city around five in the evening. The morning storm was caused by clouds that formed in the neighbouring districts and in Bangladesh. The evening one, on the other hand, originated across several south Bengal districts and was a classical nor’wester, said the Regional Meteorological Centre (RMC).




It was the thickness of the afternoon cloud-mass that cut out sunlight almost completely, leaving the city dark. It forced streetlights to be switched on and slowed down traffic movement.

“It was the thickness of the cloud and the fact that it hardly moved for hours that resulted in the darkness. The cloud hung low over the city for more than three hours. Small clouds that had originated in East Burdwan, East Midnapore, North and South 24 Parganas, Hooghly and Howrah merged to form a wide and thick mass that covered Kolkata,” said RMC director G K Das.

He added that such localized cloud masses were common in the weeks preceding the arrival of monsoon. “Pre Monsoon cloud formations are smaller and more localized. Since the heating gets reduced in the Jharkhand area – where nor’westers originate – clouds developing in the areas closer to the city converge to trigger thunderstorms,” explained Das.

The morning thunderstorm, too, was a result of localized clouds and those which had formed in neighbouring Bangladesh. While it had little impact on the temperature, the afternoon cloud cover pulled the mercury down by about 5°C. The temperature dropped to 27°C around 2pm. According to a private weather forecasting service, mercury dropped to 26°C in the evening and the RealFeel temperature was 32°C. Friday’s thunderstorms took the tally for the month to five. The city has received three squalls this month.

Even though the temperature dropped, the thundershower failed to have an impact on the humidity. The city recorded a maximum relative humidity of 92% while the minimum was a steep 72%. A steady incursion of moisture from the sea was responsible for the conditions. “This keeps the chances of further thunderstorms alive,” said Das.