40 mm rain brings mercury down by 7°C

Kolkata: An 88 kmph squall swept through Kolkata on Friday afternoon that brought much-needed relief to the city as the temperature nosedived by 7°C. Accompanied by an intense spell of rain and thunderstorm, the season’s most powerful nor’wester also left a trail of destruction in its tail.

While the morning started on a sunny note, dark, ominous clouds began gathering over the city’s skyline a little around 2 pm. Shortly after the IMD issued a red warning for Kolkata along with neighbouring North and South 24 Parganas, the nor’wester crashed onto the city around 2.40 pm. Alipore recorded the squall hitting the city from the northwesterly direction with a maximum speed reaching 88 km/h, maintaining this wind speed at least for two minutes between 2.45 and 2.47 pm. Prior to this, another squall hit Dum Dum from the same direction with a maximum speed reaching 74 km/h.

The mercury instantly plunged by 7°C within an hour of the nor’wester, with the temperature plummeting to 27°C from 34°C. Alipore recorded rainfall of about 40 mm during the spell that lasted about an hour. Some parts of the city briefly encountered waterlogging. But traffic movement continued to be affected where trees fell in major thoroughfares. The Met officials expect a further dip in mercury by Saturday.

“This was the most powerful squall of the season. At 88 km/h, it was very potent and destructive, strong enough to uproot trees in the city. Very potent thunderstorm cells and highly intense cloud were main reasons for the sharp spell and gusty wind and the thunderclaps,” said HR Biswas, head at IMD’s Regional Meteorological Centre Kolkata.

The 40 mm rain is also the month’s highest single-day rain amount so far. The total monthly rain count this May has gone up to around 165 mm so far, which has already surpassed the normal rain count of May, which is estimated to be around 118 mm. Kolkata has also recorded rain on 11 days this May against a climatological normal of 6.2 rainy days.

Data from the KMC drainage pumping stations showed a north-south divide, with south Kolkata recording heavier rainfall than north. According to a KMC source, Jodhpur Park drainage pumping station recorded the highest rainfall in an hour, 68 mm, between 1.45 pm and 2.45 pm. Other pumping stations like Ballygunge (50 mm), Kalighat (51 mm), Kudghat (52 mm), Mominpore (42 mm), Behala Flying Club (53 mm) made the task of flushing out storm difficult. Heavy-duty pumps were operated without a break.

Residents of Amherst Street, Keshab Sen Street, Thanthania, College Street, Bidhan Sarani, however, experienced waterlogging due to the construction of a drainage pumping station at Hrishikesh Park.

“We can expect some amount of rain Saturday also, but the chance is only about 40%. Hence even if it rains, it will be of less intensity,” said Biswas.