Cold snap, dense fog paralyse north India

AIr pollution surged into the wicked category in new delhi on sabbatum patch blinding murk and frigid temperatures swept much of northern India and disrupted air, road and rail traffic across 10 states as authorities issued red and orange alerts for swathes of the Indo-Gangetic plains.The maximum temperature plunged to 16.9 degrees Celsius — 5.3 degrees below normal and the season’s coldest morning yet — meeting the criteria for a cold day. Delhi’s air quality index (AQI) climbed to 410 at 11pm, breaching the severe threshold.A satellite image captured at 9am revealed the scale of the crisis: a continuous band of fog stretching from the Kashmir valley through Punjab, Haryana, Delhi, Uttarakhand, Uttar Pradesh, Bihar, Jharkhand and West Bengal into parts of Madhya Pradesh — blanketing one of the most densely populated regions in the world.At Delhi airport, where flight operations have suffered disruptions for the fifth consecutive day, 66 arrivals and 63 departures were cancelled.Data from Flightradar24 showed that by Saturday evening, 220 arrivals and over 400 departure flights had faced delays during the day, with average delay time being over 30 minutes.The Airports Authority of India issued a weather advisory warning that reduced visibility due to fog across northern India may impact flight operations at select airports, potentially leading to delays or disruptions. “Passengers are encouraged to stay in regular contact with their respective airlines for real-time flight updates,” AAI said, adding that dedicated passenger facilitation teams have been deployed.The Union road transport ministry sent text messages to holders of driving licenses and registered vehicles, urging them to take precautions while driving in foggy conditions — advisories that come days after a number of vehicle pile-ups on expressways due to low visibility.“For the past for or five days, the fog has intensified, because of which the Taj Mahal is also not visible. This is also affecting the number of tourists who come to visit the Taj,” an Agra resident told news agency ANI.A wave of delays – stretching as long as four to six hours – also hit New Delhi Railway Station, with several long-distance and premium services, especially those connecting northern and eastern cities, arriving hours behind schedule.Meanwhile, three people died and three were injured after being hit by a train amid dense fog on Saturday, while travelling to attend Prime Minister Narendra Modi’s rally at Taherpur in West Bengal’s Nadia district, a senior official told news agency PTI.Modi was unable to eventually land at the rally value and addressed it over video after low visibility prevented his helicopter from landing.The conditions stem from a subtropical westerly jet stream with core winds reaching 105 knots — approximately 195 kilometres per hour — at 12.6km above mean sea level over northern India, officials said. “The westerly jet stream contributes to cold day conditions over several parts of north India,” said M Mohapatra, director general of the IMD.The jet stream influences the path of western disturbances, causing cold air incursion. Dense fog limits solar radiation. “Together, they are causing cold day conditions,” said OP Sreejith, scientist and head of the Climate Monitoring and Prediction Group at IMD.A cold day is declared when temperatures fall below 10°C and the maximum temperature remains 4.5 to 6.4 degrees below normal. A severe cold day occurs when the departure exceeds 6.5 degrees.Unlike typical cold waves that affect nighttime temperatures, cold day conditions pose unique public health risks by limiting solar radiation during daytime hours when people are typically outside their homes.“Cold day conditions are expected to be observed on Sunday as well,” said an IMD official who asked not to be named, adding that the maximum is expected to be around 16-18°C and the minimum between 7 and 9°C.IMD issued a red alert (highest level) for Uttar Pradesh warning that fog and severe cold day conditions will persist through December 24.A western disturbance lies as a cyclonic circulation over Central Iran in the lower and middle tropospheric levels, while another cyclonic circulation hovers over the Gulf of Mannar.The weather office advised people to take precautions during early morning hours and urged authorities to remain alert as low visibility could disrupt road, rail and air traffic across the affected region.For Sunday, IMD issued orange alerts — the second-highest warning level — across large parts of Uttar Pradesh, Haryana, Chandigarh and Delhi for dense to very dense fog conditions, asking authorities and residents to be prepared for severe disruptions.Similar orange-level warnings were issued for cold day to severe cold day conditions across Uttarakhand and parts of Uttar Pradesh, where maximum temperatures are forecast to remain 4.5 to 6.5 degrees or more below normal.The weather office warned that while conditions may ease briefly, dense to very dense fog is forecast to return from December 25-27 across isolated pockets of Punjab, Haryana and both western and eastern Uttar Pradesh, indicating the crisis will persist well into the final week of December.