Localized showers keep mercury on tight leash

KOLKATA: The monsoon may be on a ‘break’ in Met parlance but localized rainfall continued to pull the mercury down and gave respite to Kolkatans from stifling heat on Thursday. The weathermen expect similar showers to keep the heat at bay till the monsoon currents gather steam again. There is a possibility of the monsoon returning with a renewed force by this weekend.

“We are expecting the monsoon currents to revive and gather momentum between June 23 and 25. Till then, we have to be content with localized thundershowers, like the ones that have been happening in and around the city over the past two days,” said Sanjib Chattopadhyay, deputy director general (meteorology) at the Regional Meteorological Centre (RMC), Kolkata.


The northern arm of the southwest monsoon has not progressed after June 12, a day after the monsoon’s officially arrived in the city. The sudden lull after that had pushed the mercury up to uncomfortable levels. The maximum temperature had soared past 40°C on June 18. The extreme heat and humid conditions had become a major concern with many schools deciding to suspend classes till the situation improved.

However, sharp shower spells in the past two days have stalled the mercury run. The maximum temperature climbed down on Thursday to 34.6°C. At 53.4, the discomfort index, which is the impact of heat and humidity on a human, was also within the normal limit. Once it crosses 55, the weather becomes intolerable.


“Three conditions — heat on the ground, abundant moisture and instability in the cloud dynamics – are required for thundershowers. Right now, all these conditions prevail to trigger more thundershower spells to keep the mercury under check,” said AK Sen, scientist at the RMC, Kolkata.


On Thursday, while most parts of the city witnessed thundershower spells, Kalighat recorded the maximum rainfall of 30mm between noon and 1pm. Belgachhia, on the northern fringes, recorded 23mm during the same duration. The rest of the city had to be content with rain measuring between 7mm to 15mm.


This uneven distribution of rain, according to meteorologists, was because the rain was triggered by local cloud formation. Unlike the monsoon rain pattern, which is widespread, the cloud size, height and maturity differ from one locality to another when thundercells are formed locally.