Many parts of northwest India are recording significantly below normal temperatures, according to India Meteorological Department (IMD). Cold wave and cold day conditions are likely to persist over northwest India till the weekend.
Several towns and cities in northwest India recorded low minimum temperatures on Wednesday. Churu recorded 2.1 degrees C (°C), 4.9°C below normal; Udaipur 2.6°C, 5.4°C below normal; Kota 6.5°C, 6.5°C below normal; and Guna 4.5°C, 5.5°C. Delhi recorded a minimum temperature of 5.4°C, 3.4°C below normal and a maximum temperature of 21.5°C, 1°C below normal on Wednesday. On Thursday, Delhi recorded shallow fog with less than 500 metres visibility this morning.
At 5.30 am, visibility at Ambala, Lucknow, and Varanasi was less than 25m each; Bahraich, Sultanpur, Patna, Gaya, Bhagalpur, Purnea was less than 50m each; Patiala, Bareilly, Gorakhpur, Kailashahar, Agartala was less than 200m; Palam and Safdarjung: 500m each.
“Till around February 15, it’s not uncommon to record cold waves or cold day conditions but this winter has been particularly cold. October was the coldest in the past 58 years, November was the coldest in 71 years, December was fine but in January, we are consistently seeing minimum temperatures to be 3-4°C below normal which could be an effect of La Nina, a global phenomenon. The minimum temperature has dipped to 1.1°C once and 2.2°C twice this month. This week, the minimum temperature over Delhi will hover around 4-5°C,” said Kuldeep Shrivastava, head, regional weather forecasting centre.
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“Another Western Disturbance is likely to bring snowfall to the Western Himalayan region from February 1 and may bring light rain to Delhi on February 3 following which, minimum temperatures are likely to fall again,” he added.
Cold, dry north-westerly winds are blowing over the northern plains and adjoining parts of central India during the next 3-4 days. Under its influence, cold day to severe cold day conditions are likely in isolated/some pockets over Uttarakhand, Uttar Pradesh and Bihar during the next 2-3 days and over Madhya Pradesh during the next 24 hours.
Cold wave to severe cold wave conditions are likely in many pockets over Punjab, Haryana and Chandigarh during the next 3-4 days; the condition will improve thereafter. Cold wave conditions are likely in isolated pockets over Uttar Pradesh, Rajasthan, Madhya Pradesh, Saurashtra and Kutch during the next 3-4 days. Ground frost conditions are very likely over Punjab, Haryana and north Rajasthan during the next two days.
Dense to very dense fog is likely in some pockets over Uttarakhand, Punjab, Haryana, Chandigarh and Uttar Pradesh during the next 3-4 days. Dense fog is also very likely over Bihar, sub-Himalayan West Bengal, Sikkim, Assam, Meghalaya and Tripura during the next 2-3 days; over north Madhya Pradesh during the next 24 hours and over Odisha during January 29 to 31.
A fresh Western Disturbance is likely to affect Western Himalayan region from February 1 onwards. Under its influence, scattered rain or snow with moderate thunderstorm and lightning is likely over the Western Himalayan region during February 1 to 3.
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, while La Niña has the opposite effect. In India, for example, El Nino is associated with drought or weak monsoon while La Nina is associated with strong monsoon and above average rains and colder winters.
IMD, in its seasonal outlook for winter released in November, 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. The diurnal temperature variation (difference between day and night temperatures) is likely to be high in most subdivisions of north, northwest, central and a few subdivisions of east India. But many parts of NW India are recording both cold day and nights this winter.
According to IMD, a cold day or severe cold day is classified as such on two parameters—a minimum temperature of under 10 degrees and maximum temperature of 4.5°C or 6.4°C below normal. A cold wave occurs in the plains when the minimum temperature is 10°C or below and/or is 4.5 notches less than the season’s normal for two consecutive days. A cold wave is also declared when the minimum temperature is less than 4°C in the plains.