Delhi recorded the season’s lowest temperature at 1.6 degrees Celsius on Friday, according to Regional Meteorological Centre. There was very dense fog in Palam with 0 visibility till 7am. After 7am, visibility improved to around 150 metres.
Many parts of the northwestern plains have recorded sub zero or near 0°C minimum temperatures in the last couple of days.
On Thursday for example, Hisar and Narnaul in Haryana recorded -1.2°C and 0.5°C respectively; Bhatinda and Ballowal in Punjab recorded 0°C and 0.2°C respectively; Sikar and Pilani in east Rajasthan also recorded 0°C and 0.2°C respectively while Churu in west Rajasthan recorded -1.3°C. Pantnagar in Uttarakhand, Una in Himachal Pradesh recorded 0.1°C and 0.5°C, respectively.
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While many of these places do record 0°C during most winters, this year the cold is definitely severe, scientists said.
After December 12, western disturbances mostly affected the Western Himalayan region; under their influence, thee was significant snowfall and rainfall over Jammu and Kashmir and Himachal Pradesh. “After the WD, cold northwesterly winds are blowing over Delhi NCR from Jammu and Kashmir and Himachal Pradesh. Uplifted fog cover over Punjab and Haryana is also making it colder. The effect of La Niña, a global meteorological phenomenon, also contributed to fall in temperatures over northwest India this year,” said Kuldeep Shrivastava, head, regional weather forecasting centre.
A fresh active western disturbance likely to affect the western Himalayan region and adjoining plains from January 3 onwards. It is likely to cause light to moderate snowfall over the western Himalayan region between January 3 and 6. Due to interaction between the western disturbance and lower level easterlies from Bay of Bengal, scattered to fairly widespread rainfall accompanied with thunderstorm or hailstorm at isolated places is likely over Punjab, Haryana, Chandigarh, Delhi, north Rajasthan, west Uttar Pradesh and northwest Madhya Pradesh during January 2 to 5 with maximum intensity on January 4 and 5, India Meteorological Department said in its Thursday bulletin.
Due to southeasterly winds over northwest and central India, minimum temperatures are likely to rise gradually by 3-5°C during the next 4 to 5 days. “Cold wave” to “severe cold wave” conditions are likely in some pockets over Himachal Pradesh, Punjab, Haryana, Chandigarh, Delhi, Uttar Pradesh, Rajasthan and west Madhya Pradesh during the next 24 hours. “Cold day” to “severe cold day” conditions are likely over some pockets of Punjab, Haryana, Chandigarh, Delhi, Uttar Pradesh and west Madhya Pradesh during the next two days and over Himachal Pradesh during the next 24 hours.
According to IMD, a “cold day” or “severe cold day” is considered based on two parameters—a minimum temperature of under 10 degrees and maximum temperature is 4.5°C or 6.4°C below normal respectively. A cold wave occurs in plains when the minimum temperature is 10°C or below and/or is 4.5 notches lesser than the season’s normal for two consecutive days. Cold wave is also declared when the minimum temperature is less than 4°C in the plains. Witnessing a cold day and cold wave together means the gap between day and night temperatures is lower than normal.
Dense to very dense fog is likely over Punjab, Haryana, Chandigarh, Delhi, Uttar Pradesh and dense fog is likely over parts of Bihar, Assam, Meghalaya, Nagaland, Manipur, Mizoram and Tripura during the next two days and over Uttarakhand, west Madhya Pradesh during the next 24 hours. Ground frost is likely over parts of Punjab, Haryana, Chandigarh, Delhi and north Rajasthan during the next 24 hours.
“During many years, minimum temperatures in Churu, Ganganagar, Bikaner, Hanumangarh, Hisar etc reach 0°C because these places are in desert regions where nights can be extremely cold but day temperatures are relatively higher so people don’t feel the bitter cold here. Climatologically we are in the peak of winter and there is an impact of cold winds from snow-clad mountains which is making even the plains reach sub-zero temperatures. Minimum temperatures are likely to rise significantly from January 2 due to the approaching western disturbance,” said Mahesh Palawat, vice-president, climate change and meteorology at Skymet Weather.
El Niño and the Southern Oscillation (ENSO) is a periodic fluctuation in sea surface temperature and the air pressure of the overlying atmosphere across the equatorial Pacific Ocean according to the National Oceanic and Atmospheric Administration (NOAA).
ENSO has a major influence on weather and climate patterns such as heavy rains, floods and drought. El Niño has a warming influence on global temperatures, whilst La Niña has the opposite effect. In India for example, El Niño is associated with drought or weak monsoon while La Niña is associated with strong monsoon and above average rains and colder winters.
“We have already said that below normal temperatures are expected over northwest India through the winter. We know that cold westerlies tend to enter inland during La Niña years which is also why winter is more pronounced,” said DS Pai, senior scientist at India Meteorological Department, Pune, had said last week explaining the impact of La Niña.