india

Updated: Dec 28, 2018 10:10 IST

Residents of Delhi have more reason to complain about the cold this month - the city is going through the longest cold spell in a December in at least 14 years, and it is likely to stay that way for some time.

Night temperatures have been lingering below 6 degrees Celsius for the past 10 days and the India Meteorological Department (IMD) has forecast that cold wave conditions will continue for at least five more days.

Data of daily temperatures since 2005 (older data wasn’t immediately available) accessed by Hindustan Times from IMD and Skymet Weather Services shows that the minimum temperature hasn’t remained below 6 degrees Celsius for more than five days at a stretch in December in the last 14 years.

On Thursday, the minimum temperature dropped to a new low since 2014, with the mercury touching 3.4 degrees Celsius, three degrees below normal. It was the coldest day of the season so far. The day was better, though - 22 degrees Celsius, which was one degree above normal.

“The minimum temperature has remained below six degrees since December 18. The night temperature is expected to remain below 5 degrees Celsius and cold wave conditions are likely to continue over the next five days at least. The lowest temperature was recorded on Thursday,” said Kuldeep Srivastava, head of the regional weather forecasting centre in Delhi.

Delhi encountered cold spells in December in 2014, 2011 and 2007, which continued for five days at the most. In the last two winters, the mercury didn’t drop below six degrees.

“This year, December has been unusually cold, both in terms of daily minimum temperature and the continuity of the cold spell. Such long cold spell hasn’t been recorded in recent times,” said BP Yadav, deputy director general of IMD.

Meteorologists from IMD said that the winter temperature in Delhi and for the whole of northwest India is governed primarily by the wind direction, which, in turn, is dependent on western disturbances.

The winds continue to blow in the same direction unless they are disturbed by some western disturbance. If they are coming from the northwest, they bring in the chill from the hills of north India. The easterly and south-easterly winds are warmer.

This winter, north-westerly winds are dominating as not a single western disturbance has hit the plains in the last fortnight. As cold winds are blowing over Delhi and other parts of northwest India, the mercury is dipping every day.

On December 12, the minimum temperature was recorded at 12.6 degrees; a fortnight later, it was down to 3.4 degrees on December 27.

“Usually at least one western disturbance hits the plains of northwest India every five, seven days during the winter. This changes the wind pattern and the mercury either dips or goes up depending from which direction the wind is coming. But this year we haven’t had a single western disturbance hitting the plains of Northwest India in the last 15 days. Hence, northwesterly winds are continuing and the mercury is dipping in tandem,” said Yadav.

Even though IMD considers December and January as the peak winter months, the latter is colder. While the mean minimum temperature in December is 8.3 degrees Celsius, it drops to 7.6 degrees Celsius in January.

“Even though January is usually colder than December, it is too early to say if January 2019 will behave the same way. Just because December was colder than usual this time, we can’t say that January too will be colder than previous years,” Yadav said.

Earlier this month, IMD forecast that the minimum temperatures in northwest India will remain between 0.50 degrees and 0.88 degrees above normal this winter with below-normal cold wave conditions.