The Capital is likely to have a colder winter than usual this year, according to India Meteorological Department scientists who cited a Pacific Ocean weather phenomenon known as La Nina, which leads to a cascading impact on global weather in winter months.
During La Nina, temperatures in central Pacific Ocean drops below normal levels, triggering wind patterns can influence weather in far away regions. This has been linked to colder than usual winters in northwest India.
“Both maximum and minimum temperatures are likely to remain around 2-2.5°C below normal this entire season. Also, since winter is setting in early with temperatures already low, the minimum is likely to fall to 5-6°C as early as December 10. This usually happens after December 20,” said Kuldeep Srivastava, head of IMD’s regional weather forecasting centre (RWFC).
He added that day temperatures, or the maximum, will begin falling in early December.
Local factors too have contributed to making days colder. Delhi has had a cloudless streak, with only one Western Disturbance so far bringing in any moisture. “When there are no clouds, the ground cools faster and the minimum temperatures stay low,” he explained.
On Friday, Delhi recorded a minimum temperature of 7.5°C, five notches below normal and the lowest November temperature in 14 years. On Saturday, it rose slightly to settle at 8.5°C, while the maximum was at 24.6°C..
In the immediate days, Srivastava said that the minimum is expected to fall further to 7°C on Sunday before a Western Disturbance on November 23 briefly causes a slight increase. Once that passes, days and nights will become colder again.
“When global conditions like La Nina are prevailing, there is a tendency for regions under northwest India to get colder,” said VK Soni of IMD’s environment monitoring research centre.
Soni added that at present, the dip in mercury is accompanied by strong winds that helps in blowing away pollutants but after November 23, wind speed is likely to reduce and trigger a deterioration in air quality.
On Saturday, the average wind speed was around 16-17kmph, and the air was in the poor zone with the 24-hour average air quality index at 4pm being 251.