Storm rips before alarm rings Radar too far, response too slow

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  • Published 15.04.10

New Delhi, April 14: Bengal found itself handicapped when a thunderstorm — neither a Nor’wester nor a cyclone but an intense weather event born over the plains of Bihar — struck Bengal on Tuesday night.

A few minutes past 11pm, Calcutta meteorologist Devendra Pradhan received an alert from his staff saying the Doppler weather radar on the 15th floor of the New Secretariat building had detected signatures of a severe thunderstorm beyond Malda.

But Pradhan had no information to predict the severity of the storm. Nor was he aware of any mechanism to reach out to the state authorities to communicate a warning that late.

Along the border of Bihar and Bengal, while Pradhan wondered about what he could do, the thunderstorm matured and dissipated its energy with devastating fury that claimed over 110 lives.

“The storm lasted about 90 minutes — and its most intense phase may have been much shorter, perhaps less than 30 minutes,” said Pradhan, a senior scientist at the weather radar station in Calcutta.

Scientists say the Calcutta radar was too far away for meaningful predictions to be made in the available time. An India Meteorological Department (IMD) project to install weather surveillance radars at several sites across the country, including Malda in Bengal, has been dogged by delays.

“A weather radar in Malda would have been within 100km of the severe thunderstorm,” said Pradhan. “We could have picked up early warning signatures 45 minutes earlier.”

The IMD was to have installed weather radars in 12 cities during the first phase of the modernisation project approved in December 2007 and scheduled for completion by March 2010. But only a single radar has been installed in Delhi, and even that is yet to become operational.

IMD director-general Ajit Tyagi told The Telegraph that one of the reasons for the delay was that civil structures for the radars had not been completed by public works departments. “In any case, Malda was to get a radar in the second phase — over the next two years,” he added.

But meteorologists point out that even with advance warnings, the mechanisms to assess the possible impacts of such thunderstorms and carry actionable warnings to the people are weak.

Along India’s coastline, the IMD has set up a satellite-based disaster warning network that connects it with district authorities and local communities — always considered at risk of cyclones from the sea.

Any prediction about likely impacts of a severe thunderstorm would require information about vulnerability of local populations — their homes and structures around them — according to meteorologists. They say storm features need to be combined with ground information — population density, the predominant type of housing and terrain — to predict impacts.

“We also need a mechanism to quickly convey information to state officials, whether it is daytime or night,” Pradhan said.

Weather scientists said the Bengal thunderstorm probably produced either a tornado or an intense downburst — both of which are associated with high-speed and potentially destructive winds. “The wind speeds can reach 100km to 120km,” a meteorologist said.

They said the Calcutta radar was too far for them to determine whether the storm had generated a tornado with a typical vortex wind flow, or a U-shaped flow of a downburst.

“Whether it was a tornado or a downburst, it would have lasted 10-30 minutes,” Pradhan said.