Why Calgary is a hot spot for severe weather

Hailstorms, tornado warnings, damaged property. They're all becoming the norm for Calgary as severe summer weather ravages the city. The reason for the ominous weather is simple: location, location, location. 

It's not bad luck, there's a very simple reason: location, location, location

Storm clouds are seen over north Calgary on Sunday at 10 p.m. (Natalie Gillis)

Lashing rain. Lightning strikes. Hailstorms. Tornado warnings. Thousands, millions or — in the case of a particularly severe June hailstorm —billions in damaged property. They're all becoming the norm for Calgary as severe summer weather ravages the city. 

It's not bad luck. The reason for the ominous weather is simple: location, location, location. 

Calgary is sandwiched between high elevation winds from the mountains, cold winds from the north and humidity from the south. It's the perfect recipe for serious storms.

"If you had to pick a place in the country that's going to have this kind of weather, it's Calgary," said Shawn Marshall, a climatology expert from the University of Calgary.

The height of the clouds and temperature of the winds determine whether a storm aggregates, and how bad it gets.

When those three wind patterns collide, they can form a volatile weather system that meteorologists call an "upper trough" — since it creates peak and valley shapes.

Those weather patterns usually drift onward after a few days, but Environment Canada says other strong winds from the rest of Canada currently have halted the movement of the trough and it's hovering over Calgary. 

Storm system hanging around

"We've been under this upper trough for the majority of the last three weeks and that's been causing the increased frequency in those storms," Blaine Lowry, a warning preparedness meteorologist with Environment Canada, explained. 

That's consistent with Marshall's read of the situation. 

"It's kind of locked into that pattern right now. And that can kind of create this blocking, or you can get stuck like this for weeks even months." 

This summer's weather isn't unprecedented, but both experts say it's oddly strong for so early in the season. 

Calgary has seen a spate of severe thunderstorm watches and tornado warnings this year.

A storm in mid-June was particularly devastating, shredding vinyl siding, smashing windshields and flooding major roadways. The Insurance Bureau of Canada estimated the insured damage at $1.2 billion or more.

Less than a week later, the city was walloped a second time. Then heavy rain and hail came yet again this week. 

On Sunday, the city was hit with a tornado warning. 

"That storm was quite intense as it pushed through areas just northeast of the city and impacted the far northeastern neighbourhoods that were already hit by that major hailstorm earlier on in June," said Kyle Brittain, Calgary bureau chief for The Weather Network.

He can't fully explain why the northeast keeps getting pummelled, when in the past most hailstorms hit the northwest part of the city.

"It's very interesting to see, it's like, 'Really? the northeast is getting hit yet again?'" he said.

On Tuesday came more tornado warnings, this time for the area east of the city. Environment Canada later confirmed four weak twisters touched down but didn't cause any damage. 

Brittain said all that rain in June made it the eighth wettest June on record in Calgary.

"That moisture that we've been receiving has been adding to the fuel of the storms," he said. "And of course the other main reason is the jet stream pattern, which has been setting up in a way that's also favourable for severe storms."

Prepare for a wet summer

Experts estimate there will likely be more severe storms dotted throughout the coming months. Environment Canada's long-term forecast for Calgary is projecting a wetter-than-normal summer.

"Anytime through July and August, people want to be prepared and have a plan for what they're going to do if storms affect their area," Lowry said.

Severe weather isn't a stranger to Calgary, but the frequency and ferocity of the storms show a troubling long-term pattern for one earth sciences professor. 

"We are witnessing probably the effect of climate change because these severe weather conditions are generally caused by warm strong wind," said Israel Dunmade at Mount Royal University. 

The long-term forecasts do show some breaks in the storm patterns — so the weather experts suggest taking full advantage of them. 

"We can hope that it can get to some sort of more normal summer weather for July and August before our too-short summer ends here in Calgary," Marshall concluded.


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