No rain relief in sight, missing Kalbaisakhi adds to discomfort
Times of India | 18 April 2024
Kolkata: The absence of any system that can trigger thundershowers has left Kolkata parched, said Met experts. While the city expects to get frequent nor’westers in April and May, before the arrival of pre-monsoon and monsoon showers, this time, it has experienced only a single thundershower in the first week of April. Additionally, there is no rain on the Met radar for the next several days.
According to weather scientists, a few important conditions that can cook up nor’westers in Kolkata around this time of the year include abundant moisture incursion from the Bay of Bengal, heating and convection that pushes the moisture into the upper air to form thunderclouds. Apart from heating, none of the other conditions — including a system like a cyclonic circulation or a trough line, which could indicate rain respite for the city — are present at the moment.
“While moisture, heating and convection are important factors for cloud formation and to precipitate thundershowers, the moisture at the lower level at present is almost absent since we are getting dry, westerly-to-northwesterly winds,” said H R Biswas, head of the weather section at RMC Kolkata.
Also known as Kalbaisakhi, nor’westers generally strike in the afternoons or evenings. Thick, dark, potent clouds appear, triggering thundershowers. Sometimes accompanied by a high wind speed, they can cause sharp torrential rain and squalls.
According to IMD’s evaluation under normal conditions, Kolkata gets a mean total of 55 mm rain in April while the average number of rain days in Kolkata during the same month should be 3.2 days. While average number of squalls for April is 1.9, there has been no squall this month.
This April, the city got rain only on April 7, when the Alipore Met office recorded a rainfall of only 0.5 mm. April 2023 had rain on four days with a cumulative rain of 50 mm. “Last April, three out of the four rainy days happened towards the fag end of the month. We still have about two weeks left this month to come to a conclusive monthly analysis,” Biswas said.