A prolonged dry spell, billed “unusual” by a Met official and one that has gripped much of the Indian mainland, has not spared Kolkata.
Into the second week of April, the city is still waiting for the first squall of the season. There has not been any rain either.
“It is quite unusual. Normally, the city gets a couple of squalls by the end of March. April also sees three to four squalls. But Kolkata is not alone. Entire south Bengal and swathes of mainland India are going through a dry phase,” said G.K. Das, director of the Indian Meteorological Department, Kolkata.
“Dry northwesterly winds are dominant in the mainland. The winds are relatively cold while originating in Kashmir. But by the time they reach south Bengal, the winds are quite hot.”
The temperature in Kolkata is relatively lower compared to western districts, where the mercury is hovering around 40 degrees.
The convergence of moisture-laden easterly winds from the Bay of Bengal and hot and dry winds from the northwestern parts of the country leads to the formation of thunderclouds that trigger squalls in south Bengal in summer.
When the clouds form over the Chhotanagpur plateau, they keep moving east. By the time they reach Kolkata, the moisture from the Bay feeds the clouds, making them stronger.
This year, the moisture-laden easterly winds from the Bay are not moving into the mainland in the absence of a conducive weather system over Bihar or Jharkhand. The winds are moving towards north Bengal and Northeast, just touching Kolkata.
As a result, north Bengal is witnessing heavy rainfall but south Bengal is dry, said Met officials.
Western districts like Jhargram and Paschim Medinipur have had one or two squalls but they were brief and localised, said Met officials.
“Kolkata has been receiving some easterly winds. There are some clouds but not enough to trigger rain,” said Das.
The weather in Kolkata has been hot and humid over the past few days. The maximum temperature has been around 34 degrees, a notch below usual.
The minimum relative humidity has been over 50 per cent.
A partial cloud cover is behind the maximum temperature staying slightly below average, said a Met official.
The days have been breezy, especially in the late afternoon and evening.
The speed of the easterly winds in their path from the Bay to the Himalayas is also crucial, said Das.
“The speed is over 30kmph in Kolkata, around 10kmph in Bangladesh and around 5kmph by the time they reach north Bengal. The slower the winds, more chances of formation of thunderclouds,” he said.
“The city is likely to see similar weather over the next few days. Some parts of south Bengal may get some rain but it is unlikely in Kolkata,” said Das.