Punjab, Haryana, Chandigarh, Delhi, Uttar Pradesh and Rajasthan will be affected
The ongoing ‘cold days’ will intensify into a ‘cold wave’ conditions from December 25, 2019 in several parts of north and north-west India, including Punjab, Haryana, Chandigarh, Delhi and Uttar Pradesh as well as Rajasthan, according to India Meteorological Department (IMD).
The weather agency's cutoff for such conditions is a minimum temperature of at most 10 degrees Celsius for the plains and 0°C for hilly areas. A cold day is defined on the basis of maximum day temperature while a cold wave is defined by looking at minimum temperatures recorded on two consecutive nights.
The departures in temperatures for both extreme events are 4.5-6.4°C below normal. When the departure exceeds 6.5°C, severe conditions are declared.
For a cold wave, apart from this, another parameter is the absolute minimum temperatures recorded for two consecutive days which has to be equal or below 4°C for the plains. Severe conditions are declared when the minimum goes below 2°C.
Why the chill
The IMD's weekly update read:
“In the past week, cold day to severe cold day conditions had been reported at most places over Punjab, Haryana, Chandigarh, Delhi, western Uttar Pradesh and Rajasthan on two days each; at many places over Punjab, Haryana, Chandigarh, Delhi and Uttar Pradesh on one day; at a few places over western Madhya Pradesh on one day; at isolated places over eastern Madhya Pradesh, eastern Uttar Pradesh, Jammu & Kashmir and Himachal Pradesh on one day each during the week.”
Delhi recorded a maximum temperature of 12.9°C on December 17 — the lowest in 16 years, since 12.6°C on December 25, 2003.
The reason for these cold days was a low-lying cloud cover over the north Indian plains, which could have been caused by the moisture incursion caused by the incoming western disturbances and the induced cyclonic circulations over the region since the beginning of December. This has also caused significant precipitation, both snow and rain, in the region which preceded the cold day conditions in many places.
In the week from December 12-18, the country as a whole received 183 per cent excess precipitation while north-west India received 448 per cent precipitation more than it receives during this time of the year. In fact, the overall post monsoon (after October 1) precipitation in the country has also been high at 35 per cent above normal.
North-west India has received the highest at 121 per cent more than normal. This comes after active south west monsoon and north east monsoon seasons in the country and the abatement of the weak El Nino conditions in the eastern Pacific Ocean. This moisture incursion has also caused fog conditions, which combined with pollutants have caused smog events, bringing down air quality in many North Indian cities, especially Delhi and the National Capital Region.
The current conditions have occurred after the IMD had declared in November that the winter season will be warmer than usual, especially for the cold wave regions of the country. It had made a similar prediction last year as well after which northern India had seen one of its coldest winters.
But the reasons for the cold wave conditions in the last season was the lack of strong western disturbances in the region in December, which had caused the cold wave to stick around while the cold day conditions this year have come with the western disturbances.
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