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Celsius dips, only to rise

Thursday was the coldest day of the season as winter continued to operate in short spells from the North Wind end, with every burst of cold coming to an abrupt end courtesy a warm period.

The minimum temperature slumped a good four degrees in the past two days as Calcutta recorded its lowest temperature of the season, 11.3 degrees Celsius.

But that might not allow you to pull out your trendy trench coat or the knitted stole for the Eveready Calcutta Derby Stake 2013-14 Grade I, held in association with The Telegraph on Sunday, at the Royal Calcutta Turf Club. For, the weatherman expects the mercury to shoot up from Friday.

In the 15 days since December 26, the minimum temperature dropped below normal three times but on all three occasions the cold spell did not sustain beyond two to three days. (See chart)

According to forecasts, the minimum would climb back to 12 degrees Celsius on Friday and be in the range of 14 to 15 degrees over the weekend.

This is in keeping with the trend over the past fortnight of the minimum fluctuating rapidly, something that meteorologists said was very unusual.

“Usually in late December and January, when there is a cold spell in Calcutta and its surroundings, the chilly winds sustain for at least five days. But this year, due to various causes, foremost among them the position of Western Disturbances that have hit north India, the Northerly winds have been blocked every two to three days,” said G.K. Das, meteorologist at the India Meteorological Department, Calcutta.

As the Western Disturbance brings moisture in its wake, there is a temporary rise in temperature where it is positioned. “What has gone against sustained cold in the northern plains, and as a result in the eastern states of Bengal, Bihar and Jharkhand, is that the Western Disturbances have blown over the north Himalayas instead of adopting a more southern trajectory that is usual,” said B.K. Bandopadhyay, deputy director general, IMD, Delhi.

As a result, the chilly winds in north India have been irregular. A direct fallout has been that Calcutta and its surrounding areas, where the cold is brought in by winds passing over the northern plains, has felt its chill in short phases.

Meteorologists said there was still time for Calcutta to get really cold as the trajectory of Western Disturbances might change.

“There is a cyclonic circulation over Rajasthan, which is a system induced by a Western Disturbance, and a high pressure belt near Bihar. The cyclonic circulation is likely to travel east and push the high pressure belt to the Bay of Bengal. Both systems would result in moisture incursion to Calcutta and that is why the temperature would remain high for the next four to five days,” said a weather scientist of IMD Calcutta.

Once these two systems clear around Monday or Tuesday, the chill could return to Calcutta.

Last year, the coldest day was January 9 when Calcutta recorded 9 degrees Celsius.