The gusts that hit Ottawa in May were equivalent to an EF-2 tornado

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The May 21 storm battered parts of southern Ottawa with wind gusts that likely reached 190 kilometers per hour, much stronger than Environment and Climate Change Canada’s early estimates.

The gusts would be equivalent to the strength of an EF-2 tornado, Western University researchers believe.

“It’s a bit stronger” than a downburst from a typical thunderstorm, said Western engineering professor Greg Kopp.

“I would say Ottawa was really unlucky.

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Immediately after the storm, Environment Canada reported maximum gusts of 120 kilometers per hour in eastern Ontario and up to 145 km/h in Quebec. But these figures are limited to the gusts that blew on the weather stations.

Kopp holds a Research Chair in Severe Storm Engineering – designing buildings to survive catastrophic weather conditions. His group searched more broadly in the community.

“We do this indirectly by looking at the damage,” he said – the same technique that is used to calculate the strength of a tornado after the fact.

“We send teams out and look at what’s damaged, what’s not, and assess it on that scale.”

In Ottawa, that meant examining lots of downed trees, but also buildings and utility poles. “For me, it was a very big event for the trees.”

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This survey suggests that the areas with the highest wind speeds are generally east of the Ottawa International Airport near Hunt Club Road.

The culprits were downbursts. “The way I describe it as an engineer is that it’s cold air falling from the sky,” he said. The heat makes the air rise, but “which eventually falls to the ground. Downbursts form in a storm when a cold part of it descends.

Cold air descends quickly, then hits the ground and quickly rolls sideways.

His group creates a map of the storm’s strength as it travels from southwestern Ontario to Quebec. It’s a big job: there are thousands of square miles to examine because the storm was broad-based and extended a long distance.

“It’s a challenge for our team to ride such a large and extensive storm.”

He hopes to have a fuller picture of the storm in a few months.

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