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When dust gathers storm

P Anima | Updated on May 25, 2018

Run for cover: This May, dust storms coincided with western disturbances, with deadly results - REUTERS/ ADNAN ABIDI   -  REUTERS

Dust storms and thunderstorms — natural mechanisms to abate heat — are the norm in North India as the earth skewers from April to June. Their arrival rarely raised any alarm. In fact, a couple of dust storms were seen as welcome and timely to snap ripe Dasheri mangoes off their branches. All that changed this April when menacing dust storms ravaged large parts of this region, particularly Uttar Pradesh (UP) and Rajasthan, leading to over 200 deaths since. Three severe dust storms and thunderstorms in May took the maximum toll.

What caused this natural phenomenon to turn lethal? According to the World Meteorological Organisation, “Sand and dust storms usually occur when strong winds lift large amounts of sand and dust from bare, dry soils into the atmosphere.”

Dust storms and thunderstorms, says KJ Ramesh, director general of meteorology, India Meteorological Department (IMD), are nature’s way of restoring equilibrium when hot weather conditions prevail for three to four days. Thunderstorms are normal from March to May in southern India, while dust storms continue till June in the North. They tend to be local phenomenon, rounded off by a spell of rain to pull down the temperature.

This May, however, the dust storm coincided with western disturbances, with deadly results. “The local thunderstorms are known as kaal baisakhi. The western disturbances are rain-bearing systems coming in from the Mediterranean Sea, drawing moisture from the anti-cyclonic circulation from the Arabian Sea,” says Ramesh. On May 2, 7, and 13, successive passing western disturbances brought widespread rains in Punjab, eastern UP and Bihar, while in Rajasthan, a few other parts of UP, and Delhi among several places, they coincided with the local storm developments and precipitated as severe dust storms.

The storm, says Ramesh, spreads over four to five hours. “It has a growing or developing phase, precipitation and dissipation.” The IMD classifies storms depending on wind speed — ‘light’ if it is around 35 kmph, ‘moderate’ at 35-60 kmph and ‘intense’ at 70-100 kmph. However, these winds could turn into a local squall in densely inhabited areas — which proved to be the primary cause for casualties in May. A moderate storm turns severe when it passes through a dense cluster of multistorey buildings and houses separated by narrow passages that leave little room for the wind to manoeuvre.

“The resultant tunnelling effect makes the storm stronger — a 40 kmph wind can grow into an 80-100 kmph storm.” These winds can blow off roofs and uproot electric poles, set off wall collapse, fell trees and make harmless objects deadly. “Even stones used to keep the covers of water tanks in place can become lethal. So too pipes, hoardings…” says Ramesh.

UP has reported the maximum deaths, over 150, most of them caused by wall collapse and falling trees. “Most of the deaths on May 2-3 resulted when kuccha houses and tin sheds collapsed while people were asleep,” says Gaurav Dayal, district magistrate, Agra — the worst-affected district. “Around 7,000 electric poles were uprooted. We have just finished restoring electricity everywhere,” adds Dayal. The intensity of the storms has taken everyone by surprise. “Even the old men I spoke to had not seen such a severe storm in their lifetime,” says Dayal.

In neighbouring Rajasthan, dust storms are no aberration. Yet, the State relief commissioner Hemant Kumar Gera says old-timers recall witnessing such ravaging storms not less than 27 years ago. “People tell me similar storms had occurred the year Rajiv Gandhi was assassinated, resulting in many casualties,” says Gera over the phone.

In Rajasthan, 19 people perished in Bharatpur and Dholpur districts in the April 11 dust storm and thunderstorm. Another 35 died on the night of May 2-3 in Bharatpur, Dholpur and Alwar districts. In the first two instances, Gera points out, there were no specific warnings except the weekly IMD forecast. Further, the Doppler radar in Jaipur was not functional, hampering information inflow.

The events of May 2-3 have proved to be a turning point. Stakeholders have got together, and through meetings, discussions, advisories, awareness programmes and information dissemination, a more effective prevention mechanism is being evolved.

The National Disaster Management Authority has issued a set of dos and don’ts. The guidelines are simple, but the onus is on dissemination. “The approach has become holistic since. Information from the district control rooms are passed onto collectors, who send it out through local media and WhatsApp groups. When another dust storm occurred on May 13-14, Rajasthan did not have casualties,” notes Gera.

It helped that the Doppler radar was functional again. When the storm hit Bharatpur and Alwar, Gera remembers warnings being sent out to neighbouring Dholpur. An hour’s gap — the time needed for the storm to travel — was used to send across warnings through social media. “People could take shelter and also save their cattle.”

At the IMD, criticised both for inadequate warnings and going overboard, outreach has been the focus since May 2-3. “SMS-based Nowcasts are sent out to media coordinators, who take it to local cable networks and WhatsApp groups. Pushing down the warnings from the state to the district and community levels is important,” says Ramesh.

Detecting a storm through satellite or radar is the easier part. “Detection mistakes will not happen. But predicting intensity or time and place of occurrence can only be done through Nowcast,” he says. Nowcast warnings, available at all district centres, are for weather conditions over the next two to three hours.

As people learn to take dust storms and thunderstorms seriously, Ramesh points out the warnings are always present. “Conditions develop overhead 30-40 minutes before the storm. Dark clouds pass by, visibility decreases, temperature drops drastically, sometimes by 5-7 degrees, before the storm,” says Ramesh. It is time to move towards safer places — not under a tree or bus shelters — but strong structures. Not brushing off dust storms is the key.

P Anima

Published on May 25, 2018

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