Tornadoes -- and warnings -- are on the rise, here's why

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Does it feel like you're getting more and more tornado warnings? We have a severe thunderstorm risk, including the potential for large hail and isolated tornadoes. A severe thunderstorm watch. Then, in this grey zone, you have a tornado watch.

Two tornadoes touched down between Edgerton and Dilbury Provincial Park. Whoa, look at that, right there. This tornado was 30 kilometers southeast of Winnipeg, another one 50 kilometers south of the city. Those tornado reports, watches and warnings were all issued over the past three weeks.

Tornado warnings in Canada have doubled since 2024 and the number of actual tornadoes themselves is on the rise as well. So what's causing them and are the warnings worth paying attention to? Dave Sills is the director of the Northern Tornadoes Project at the Canadian Severe Storms Lab at Western University in London, Ontario.

Dave, good morning. Good morning, Pia. Can we just start with actual tornadoes? How is this year thus far comparing with previous years?

Right. Well, 77 tornadoes across the country so far. The 30-year average is 65, so well above average. But the real story has been on the prairies. 64 tornadoes so far, you know, really midway through the season.

And we basically, if we go back to 1980, which is the beginning of our high quality data set, there's not another year like that. The closest is 62 tornadoes in 1991. So we're looking at record numbers here on the prairies.

And, you know, in the east, it's been 13 tornadoes. So really, the action has been on the prairies this year. And you said season, how far are we into tornado season? Right. Well, usually it's June, July, August, right across Canada. Those are the busiest months, which is different in the U.S.

They have different peaks because of, you know, different seasons down there. But across Canada, it's June, July, August, and with July being the peak. So we're really just, you know, halfway through the season here, and we've got big numbers already. So the big question is, why are we seeing more this year?

Well, yeah, some years you don't see nearly as many as this. But this year we've had a setup where we've had a system parked over the western U.S., a heat dome. It's been pretty persistent. And all this instability collects under that heat dome.

There's not a lot of thunderstorms right under it. But along the northern edge is where all that instability escapes and you get thunderstorms building up. And, of course, the prairies have been right under that northern edge for a long time now. And so that means they've been getting hit with wave after wave of severe storms.

And that includes tornadoes. It hasn't been the same story in the east. We've been on kind of the northeast side of that heat dome. We're seeing the effects of that heat right now.

But for most of the season, we've been on the less favorable side of that heat dome and just haven't seen the same level of storm activity. You know, the last couple of weeks, we heard it there in those news things, But my phone has had so many alerts about tornado warnings and watches.

I've been like, does this happen every year? You've told us, no, this is a big year. But I want to talk about the warning system. Where are we at in terms of the warnings?

They've doubled since 2024 as well, the warnings? You know, it's been interesting because one of the things we're doing at the Northern Tornadoes Project is we actually conduct performance assessments of the warning program. So the tornado warning program. We started this back in 2022, and we looked at 2019 to 2021.

Over those years, how well did the tornado warning program do? And the picture wasn't a very pretty one. It was a failing grade, basically. And that's using targets from Environment Canada themselves, how they measure their success.

So we knew there were improvements to be made. We made recommendations. And one of them was, statistically, you just couldn't get better unless you issued more. And when we did the report card again the next year, they had doubled the number of tornado watches, number of tornado warnings, and now they were getting a passing grade.

So that's what it took. And yes, it results in more false alarms, and those can be managed. But the main thing is not to miss the big ones. There were too many events where we'd get on site to do the survey of the damage,

and the people said, well, we didn't get a warning, or we got a warning, just as we were standing out in the street talking to the neighbours about the damage. So let me pick up on two things you said there. The first thing is, how do forecasters determine if a watch or a warning needs to be issued?

Sure. Yeah, there are definitely two phases there. One is the watch phase. As my wife likes to say, you watch for a warning. So the watch comes first.

And, you know, when you're thinking about the warning, or sorry, watch, that's when you're using computer models to get an idea of the ingredients for severe thunderstorms and possibly tornadoes coming together. And sometimes you can see that days in advance,

all those ingredients coming together. You don't know exactly where, when, or how intense, but you know roughly that, you know, there's going to be a big day. And as you get closer, you can kind of narrow that down to an area where you can issue a watch and say, okay, in the next six hours, the ingredients have come together that we could see tornadic storms here.