IMD found reasons for intense foggy cold waves in North India

The India Meteorological Department (IMD) has linked the intense foggy and cold wave conditions in North India to the absence of an active western disturbance (WD) over Northwest India, the presence of El Nino conditions, and a strong jet stream.

Few Western Disturbances this winter

Generally, Northwest India experiences the impact of 5-7 Western Disturbances (WDs) from December to January. However, this winter, we have not received any such WD. Two WDs did affect the country - one in December and another in January, but they primarily impacted Gujarat, North Maharashtra, East Rajasthan, and Madhya Pradesh.

The India Meteorological Department (IMD) has reported that from the 12th to the 17th of January, the minimum temperatures in many stations of Northwest India have been below 4°C. Since the 25th of December, the plains of Northwest India have experienced very dense fog conditions, reaching their maximum intensity and duration on the 14th. On this date, observers noted zero visibility over the entire North Indian plains from Amritsar to Dibrugarh, spanning across Haryana, Delhi, UP, and Bihar.

This severe weather is primarily due to three reasons. First, there has been a lack of any active Western Disturbance (WD) over Northwest India during the months of December and January. Typically, 5-7 WDs impact Northwest India during these months, but this winter, no such WD has been received.

The two WDs that did affect the country, one in December and another in January, had their impact mainly confined to Gujarat, North Maharashtra, East Rajasthan, and Madhya Pradesh. As a result, the Western Himalayan Region received very little precipitation (rain/snow) during December, about -80% departure from normal over the region. Similarly, there has been almost no precipitation in the region until the 17th of January.

El-Nino reduces cold wave days

Second, the lack of active WDs can also be attributed to the prevailing El-Nino conditions over the Equatorial Pacific Ocean. During El-Nino years, the number of Cold Wave days over North India is less than normal, which is evident in the lesser number of Cold Wave Days during December and January.

Third, strong Jet Stream winds of the order 250-320 kmph at about 12 km above mean sea level have been prevailing over North India for the last 5 days. This is leading to the subsidence of cold air and enhancing cold wave/cold day conditions over North India. A similar intensity of the Jet Stream is likely to continue for the next 5 days, resulting in the persistence of cold conditions over North India.

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