The current spell of dense to very dense fog across the Indo-Gangetic plains is likely to reduce during the next 2-3 days.(PTI)
The current spell of dense to very dense fog across the Indo-Gangetic plains is likely to reduce during the next 2-3 days.(PTI)

Dense fog engulfs parts of north India, mercury dips

Dense to very dense fog was recorded on Sunday over Punjab, Haryana, Uttar Pradesh and parts of Uttarakhand, Delhi and north Rajasthan. ‘Cold day’ to ‘severe cold day’ conditions occurred at most places over Punjab and Haryana and at isolated places over UP.
By Jayashree Nandi
PUBLISHED ON JAN 18, 2021 04:12 AM IST

States in the Himalayan foothills stretching from Punjab to Meghalaya recorded dense fog on Sunday, with reduced visibility over the entire region till midday.

This also led to several places in northwest India and the Indo-Gangetic Plains recording very low day temperatures as fog cover blocked the warmth from the sun.

Delhi recorded a ‘cold day’, with the Safdarjung station recording 15.3 degrees C, 5 degrees C below normal; Palam recorded 14.3 degrees C, 5.5 degrees C below normal and Lodhi road 14.4 degrees C, 5.4 degrees C below normal.

“This is the peak fog episode this year as per satellite images. On Saturday, Amritsar, Chandigarh, Delhi, Varanasi, Gaya all airports had recorded zero visibility for some time. Today (Sunday), it was slightly better but still dense. This vast layer of low cloud formation is very specific to the Indo-Gangetic region but this year its occurrence is delayed. The worst fog episodes have been recorded in El Nino years. La Nina years are associated with clear skies and cold nights but this year too we are seeing such a major fog episode,” said RK Jenamani, senior scientist, national weather forecasting centre.

Kuldeep Shrivastava, head, regional weather forecasting centre, said: “This January has been cold. We recorded 1.1 degrees C on January 1. Normally minimum temperatures dip to around 3-4 degrees C. There is a layer of uplifted fog stretching across the Himalayan foothills. This is mainly because of high relative humidity, slow winds and cold air.”

M Mohapatra, director general, IMD, said: “We predicted dense fog. Whenever an intense western disturbance passes, there is a lot of moisture in the air and the air is also cool. (A WD caused widespread snowfall in the hills and rain in the plains on January 6 and 7). These conditions are favourable for fog formation and also for development of ‘cold day’ to ‘severe cold day’ conditions. Today, there was dense fog in Punjab, Uttar Pradesh and Bihar.”

Another western disturbance is likely to bring widespread snowfall to the western Himalayan region on January 22 following which minimum and maximum temperatures will drop once again over northwest India, according to forecasts.

Dense to very dense fog was recorded on Sunday over Punjab, Haryana, Uttar Pradesh and parts of Uttarakhand, Delhi and north Rajasthan. ‘Cold day’ to ‘severe cold day’ conditions occurred at most places over Punjab and Haryana and at isolated places over UP. The lowest minimum temperature over the plains of northwest India was 1.4 degrees C recorded at Pilani in Rajasthan.

The current spell of dense to very dense fog across the Indo-Gangetic plains is likely to reduce during the next 2-3 days, with likely occurrence of dense to very dense fog in some pockets over Punjab, Haryana, Chandigarh, Delhi, Uttar Pradesh, north Rajasthan, Bihar, Sub-Himalayan West Bengal, Sikkim, Odisha, Assam, Meghalaya, Nagaland, Manipur, Mizoram and Tripura during the same period.

‘Cold day’ to ‘severe cold day’ conditions are likely in isolated pockets over Punjab, Haryana, Chandigarh and Delhi during the next 24 hours and ‘cold day’ conditions in isolated pockets over Uttar Pradesh, Bihar and West Bengal during the next two days, IMD said in its Sunday bulletin.

Currently, easterly winds are prevailing at lower levels over the plains of north India. This is likely to cause gradual rise in minimum temperatures by 2-4 degrees C over most parts of northwest India during the next 48 hours. Thereafter a reversal of wind direction is likely to westerly/northwesterly from January 20. This is likely to cause gradual fall in minimum temperatures by 2-4 degrees C during subsequent 2-3 days (January 20 to 22) over the same region, the bulletin added.

According to IMD, a cold day or a severe cold day is classified as such based on two parameters — a minimum temperature of under 10 degrees C and maximum temperature of 4.5 degrees C or 6.4 degrees C below normal, respectively. A cold wave occurs in the plains when the minimum temperature is 10 degrees Celsius or below and/or is 4.5 notches lower than the season’s normal for two consecutive days. A cold wave is also declared when the minimum temperature is less than 4 degrees C in the plains.

IMD in its seasonal outlook for winter had said nights and early mornings are likely to be chilly, recording below normal minimum temperatures over most parts of north, northwest, central and some parts of east India while day temperatures are likely to be above normal over the same regions.

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