Celsius set to dip to 12 in two days
Alipore: The coldest phase of winter is tipped to start this week with the Celsius taking a three-degree tumble to hit 12 by Thursday morning.
The forecast of chilly weather - 13.8 degrees is the lowest that the mercury has gone so far this season - came after the northwesterly wind picked up speed on Tuesday afternoon.
"A cyclonic circulation over Bangladesh had been injecting moisture into the air and preventing the flow of the cold northwesterly wind. This circulation has since gained altitude up to 1.5km from the earth's surface, paving the way for the wind to blow freely," said Ganesh Kumar Das, director of the India Meteorological Department, Calcutta.
The northwesterly wind, which originates in Kashmir, will not only be stronger but also colder, according to the weather office.
The minimum temperature has been stuck at around 15 degrees Celsius for six consecutive days. Tuesday's reading was two notches above normal. But with the northwesterly wind being unleashed, the descent of the Celsius should be quick.
Das said a trough of low pressure in Uttar Pradesh was shifting east, carrying a mass of chilly air behind it. "With the trough shifting east, this mass will start blowing over Calcuttta and its neighbourhood and the temperature will plunge."
The cold mass of wind would be released only after the trough clears out, crossing north Bengal along the way.
A trough is an imaginary line connecting two low-pressure points.
The lowest temperature this winter was recorded on December 27, but the feeling of cold did not last beyond a couple of hours.
The coldest day before that was Christmas, when the minimum temperature hit a low of 14.3 degrees.
On New Year's Day, the maximum temperature had dipped from 27 to 25 degrees Celsius but the minimum reading was two notches above normal at 15.3.
If the temperature dips as expected in two days, there is every possibility of the cold phase being a lasting one because of the absence of low-pressure zones over the Bay of Bengal. Any such zone is an impediment to the flow of the northwesterly wind.
The other factor in favour of a sustained cold phase is that the northwesterly wind is currently intense and unlikely to dry up quickly.