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Why thunderstorms have gripped north India, explained

India Today logo India Today 08-05-2018 Prabhash K Dutta


Weather is not following its own rule in North India at the moment. The amount of dust in the storms makes them a little different and also points to human interference with the weather patterns by means of excessive construction activities in the affected region.: Why thunderstorms have gripped North India, explained © Prabhash K Dutta Why thunderstorms have gripped North India, explained

The Indian Meteorological Department (IMD) has said that May 2 thunderstorms were the most lethal in six years. In terms of casualties, these were twice as deadly as second worst during the period -- nearly 130 persons were reported dead in the May 2 weather-related incidents while 65 people had died on April 21, 2015. The unstable weather condition continues over a large swathes of north and northwest India and parts of east and central India.

Weather scientists have long been linking increased frequency of storms with a rise in temperature on account of global warming. This year's summer, according to the IMD reports, has been unusual with most of the places recording up to two degree higher temperatures than the average for the season.

Rajasthan, Haryana, Punjab and parts of Jammu and Kashmir along with the neighbouring areas of Pakistan are facing the worst conditions of heat. The IMD also reported that day temperatures were appreciably above normal in some parts of Himachal Pradesh, Rajasthan, west Madhya Pradesh, Saurashtra and Kutch, Konkan and Goa, central Maharashtra, Vidarbha and coastal Karnataka, and were above normal in some parts of east Madhya Pradesh, Gujarat and Marathwada.

A trickle of moisture from the Bay of Bengal has found its way along the foothills of the Himalayas to these unstable regions. The unusually high temperature zones reacted violently when they came in contact with moisture-laden air to create spells of dust storms.

Aren't storms normal in early summers in North India?

Pre-monsoon weather in India has always been vulnerable. Late April and May are the peak time for pre-monsoon weather activities that include dust storms, thunderstorms, lightning strikes, rain and thundershowers -- from mild to severe.

As a norm, India records four to five spells of intense thunderstorms and dust storms. However, meteorologically not more than two spells of extremely severe pre-monsoon storms are usually recorded every year.

Occurrence of more than one severe storm within span of a week has been very rare in the country especially north India. As a matter of rule, severe storms don't hit the same area twice with same intensity in the same season.

What is happening now?

Weather is not following its own rule in north India at the moment. The amount of dust in the storms makes them a little different, and also points to human interference with the weather patterns by means of excessive construction activities in the affected region of North India. Construction activities are considered to be the single-most air pollution agent in Delhi and neighbouring Haryana, Rajasthan, Punjab and parts of Uttar Pradesh.

The current dust storms of North India are following patterns similar to those in central and eastern United States -- another region which have witnessed increased construction activities in recent decades. The storm winds appear to be down bursts at both the places.

Downbursts are thunderstorms characterized by intense downward air movements having huge volumes of dusts. Down bursts are known to travel up to 300-400 km before they lose energy and settle disperse after hitting ground at various places on their way. Prevalence of dry hot air in north and northwest India has aided to the intensity of down bursts during thunderstorms over the last one week.

How IMD has explained the weather condition?

The IMD issued alert for dangerous thunderstorms and dust storms across most parts of India with higher intensity in the north and northwest parts. The wind speed was expected to breach 130 kmph mark at several places.

After last week's thunderstorms, the IMD said that there were primarily four reasons that led to the volatile weather condition. These were - excessive heating (above average temperature), availability of moisture, instability in atmosphere and a trigger for the storm.

High temperatures over a vast tract intensified the storms that originated in the desert area of North West India. The North Indian plains have been witnessing higher than average temperatures. The region is receiving moisture from two sources - a disturbance over North Pakistan and adjoining Jammu and Kashmir, and easterly winds from the Bay of Bengal.

The weather condition turned into a cyclonic circulation over Haryana, which triggered the massive down bursts or dust storms accompanying thunderstorms. The cumulative effect was formation of two cloud patches over North West India. One cloud patch of thunderstorm moved North of Delhi while the other patch moved over eastern Rajasthan-southwest Uttar Pradesh. Similar weather condition still prevails.

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