Fewer western disturbances causing foggy and cold winter, says IMD

The dense fog and severe winter prevailing since December 25 over the northern plains — stretching from Punjab to Assam and across Haryana, Delhi, Uttar Pradesh and Bihar — can be attributed to a lack of active western disturbance caused by El Niño, the met department said on Thursday.

The India Meteorological Department (IMD) added that strong jet streams were also causing the cold conditions.

“Generally, five-seven western disturbances (WDs) impact Northwest India during December to January. But this winter, no such western disturbance has been received. Two affected the country this year, one in December and another in January, but their impact was mainly confined to Gujarat, north Maharashtra, East Rajasthan and Madhya Pradesh. As a result, the Western Himalayan Region has received very less precipitation (rain or snow) during the month of December, which is roughly about 80 per cent less than normal over the region,” the IMD said in a note written by senior scientists.

Similarly, this month there was almost no precipitation over the region till January 17.

“Lack of the active western disturbances can also be attributed to El Niño conditions over the Equatorial Pacific Ocean. During El Niño (La-Nino) years, the cold wave days over North India happen to be less than normal, which is visible in terms of lesser number of cold wave days during December and January,” the note said.

The IMD further said that strong jet stream winds of the order 250-320 kmph at about 12 km above mean sea level had been prevailing over North India in the last five days.

“It is leading to subsidence of cold air and enhancing cold wave/cold day conditions over North India. Similar intensity of jet stream is likely to continue during next five days, which will result in persistence of cold conditions over North India during next five days,” the IMD said.

Maximum temperatures are running below normal by 5-8° Celsius over the plains of North India since December 29 with a brief respite during January 7-8.

These temperatures went into the normal range for a brief period after January 8 due to the influence of a western disturbance. Also, the minimum temperatures have been running below 4° Celsius at many stations of Northwest India during January 12-17.