At 116kmph, faster than Aila

The Telegraph

A tree that fell near the Lake Kali temple on Southern Avenue trapped a Nissan Sunny and a Maruti Swift in the middle of the road on Wednesday evening. Three occupants of the Sunny clambered out unhurt. “Bhagwan ki kripa ki hum log bach gaye (God’s grace that we are still alive),” driver P. Thakur said later. He was driving through blinding rain and whistling winds when the tree came crashing down. The occupants of the Swift could not be contacted. Picture by Sanjoy Chattopadhyaya.

What hit Calcutta on Wednesday at 7.15pm?

The fiercest Nor’wester in at least a decade. It ripped through the city at 116km an hour — faster than Cyclone Aila that struck on May 25, 2009, by at least 6kmph. Aila’s peak speed was 120kmph but in Calcutta, it hovered around 110kmph. Nor’westers usually hit a peak speed of 50-60kmph

What made it faster and fiercer?

A taller than usual thundercloud cell that crept up on the city from the districts overnight. The column of cloud rose 18km from its base — nearly twice what is usually seen during this season

Were lives lost?

Yes. A toddler died in Howrah when the tiled roof of her home caved in. A 40-year-old cigarette vendor was killed in South 24-Parganas when a banyan tree fell on his shop

How did the city suffer?

At least 50 trees were uprooted along key roads and residential neighbourhoods. A drive through Red Road seemed like a jungle safari after the storm

Why were so many trees uprooted?

Most trees in the city do not strike deep roots because they grow on concrete and brick bases instead of soil. Many full-grown trees on the pavements of the city are “top heavy”, with little grip below the surface. The trees can be uprooted with relative ease compared to trees that grow on the Maidan, for instance

How long did the storm last?

Around five minutes from 7.15pm. The peak speed of 116km an hour lasted less than a minute. Strong winds, however, buffeted the city till around 8pm

Why did the Nor’wester cause much less devastation than Aila?

Largely because of the difference in duration and the unidirectional flow of wind, weather scientists said. Aila’s peak speed had lasted over 15 minutes, while that of the Nor’wester less than a minute. Cyclones have multidirectional windflow, which can cause severe destruction. In case of Nor’westers, the wind usually flows in a single direction. The storm on Wednesday was more intense in the central and southern parts of the city, while the north was largely spared. During Aila, almost entire Bengal, south to north, was affected. Cyclones are “titanic” weather phenomena, which drastically alter weather patterns for weeks or months. Nor’westers are “small” local phenomena, which have little impact beyond a few hours

Can the city experience more such storms this season?

IMD officials said there could be more Nor’westers in the season (April-May). But Wednesday’s intensity is rare.

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