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Domino effect of bad luck led to sinking Add to ...

Sinking a ship that has previously crossed the Atlantic and sailed through the inhospitable waters of Cape Horn takes more than a bit of bad weather.

That's just what the Concordia faced on this week: a treacherous gust known as a microburst.

The best way to imagine what a microburst looks like is to picture a fire hose pointed straight at the ground, said Roger Wakimoto, director of the National Centre for Atmospheric Research in Boulder, Colo.

"It strikes [land or water]and spreads out violently at all directions," he said. "They're very, very strong downward motions that typically come from thunderstorms."

The vertical column of air can be less than a kilometre wide, and the horizontal winds, when it hits a surface, spread out less than four kilometres.

In 2008, a microburst struck a commuter bridge during an intense storm in Montreal, knocking over transport trucks. A 1999 storm in Toronto saw a microburst rip the roof off a building.

This type of wind has caused problems for boats before, but usually affects smaller vessels, Mr. Wakimoto said. In 2004, an 11-metre water taxi capsized in Baltimore's Inner Harbour after a microburst flipped it.

A 30-foot sternwheeler - named the SciTanic - was travelling down the Tennessee River when a microburst caused it to capsize in 1984. Of the 15 people aboard, 11 were trapped inside and drowned.

Microbursts were also the cause of a number of airline crashes, until a 1985 crash that killed 114 people led to the development of microburst detection equipment.

The vessel that sank on Wednesday was caught in a domino effect of bad luck.

The captain saw bad weather coming, and expected strong winds, so he lowered some of the tall ship's 16 sails and trimmed others.

It was the right thing, Mr. Wakimoto said. But when the downdraft struck the ship, the sails that were already at an angle were pushed further down. The leverage exerted by the sails is called a heeling force, and creates a kind of lever pulling at the ship.

Downdraft winds can be extremely high, and the velocity changes dramatically in a very short period of time.

"A ship at sea, it's a pretty rare occurrence that those kind of winds could capsize it," Mr. Wakimoto said. "It has to be very, very strong."

With reports from Jeffrey Simpson

****

The SV Concordia sank on Feb. 17, when the high-speed winds of a microburst caught the sails of the ship and tipped it over.

MICROBURST: Cool air descends and accelerates as it approaches the water. It then spreads out in all directions at high speeds.

HEELING: A sailing term for the boat ìtippingî to one side, caused by the force of the wind on the sails.

TRISH McALASTER / THE GLOBE AND MAIL

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