Minnesota sees its most active start to severe weather season in 4 years
A tornadic thunderstorm is seen from MnDOT traffic cameras as it moves south and east of Rochester on Friday. This view is looking east from U.S. Highway 63 in south Rochester.
Minnesota Department of Transportation
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Audio transcript
NINA MOINI: As we heard earlier in the show, residents in southeastern Minnesota are still cleaning up after several tornadoes passed through this last weekend. MPR News meteorologist Sven Sundgaard says it's been an active start to severe weather season with several tornadoes. For more on what could be ahead for the rest of the season, Sven joins me now.
Thanks for being with us, Sven.
SVEN SUNGAARD: Absolutely, Nina.
NINA MOINI: Yeah, this is so important. I don't know if you heard us talking with the Sheriff from Olmsted County earlier in the show, but to already have these tornadoes, how many tornadoes have we had already, and how does it line up to other years?
SVEN SUNGAARD: Yeah, we've had 11 tornado reports so far this April season already. Five of those were just from Friday, two of which were EF2s on Friday. So that's pretty incredible. Minnesota, we tend to see the smaller side of those tornadoes. So those are significant tornadoes, one of which, around Stewartville and Marion, packed 130-mile-an-hour winds and was on the ground for 10 miles. So that's a longer-track tornado. We average only one tornado in the month of April in Minnesota, so that's already way above normal. This is our most active start to the severe weather season in four years.
68 total severe weather reports, which includes large hail and wind, of course, too. And of course, last year was an active season too, but it was pretty brief. Most of last year's tornadoes and activity came just in the month of June. People might remember we had about three weeks there that were pretty bumpy.
NINA MOINI: Yeah. So I think people are wondering like, why is this happening? And does winter weather affect this or the type of winter we had?
SVEN SUNGAARD: Yeah, it can. Severe weather season starts in about February, March in the deep South as things start to warm up there. Spring, of course, gets there earlier and there's still a lot of cold left in the Northern states. And it's that clash of air masses that creates thunderstorms and the potential for severe weather. And this winter was a little odd. People might remember we had some occasional cold, but overall, it was pretty close to average. But we had an unusually strong polar vortex. But it was also very disturbed. We had a lack of Arctic sea ice that helped contribute to that, a La Niña pattern that helped contribute to things.
And so there's been this leftover blobs of cold air. basically, most of Canada and Alaska have seen very cold temperatures March into early April, and so that lingering cold, combined with some pretty hot weather in the South, has created an unusual temperature contrast. You might remember a couple of weeks ago the Southwest seeing record temperatures, so there's plenty of heat and moisture in the Southern part of the country. And we've just been in that collision course. It's finally been migrating North. And so it's been Minnesota and especially Wisconsin's turn.
Southern Wisconsin has had four different episodes of severe weather last week, about double what we've seen. So we think it's crazy here, but it's been even worse to our east.
NINA MOINI: So what does that show, if anything, for spring and summer and how that might go down?
SVEN SUNGAARD: Yeah, so spent a lot of the weekend deep diving into the data, and there really aren't many correlations between April and June. June is our peak month, usually for severe weather, but there isn't much of a correlation there. Typically what happens in Minnesota is we'll get one month that is particularly active, and then the rest of the season is average or even below average. So this might be the one month or maybe June or July could be more active again. But what we have been seeing is that we've been seeing this above-normal precip for April. That was expected.
And whenever we see above-normal precip in the spring and summer months, that usually translates to an uptick in severe weather too. So Climate Prediction Center forecasting equal chances of above or below normal precip and temperatures for May. So it might be a little calmer, but this pattern might linger for another couple of weeks yet.
NINA MOINI: What about trying to assess some of the trends? When you look at the last decade or so, what are you seeing that's shifted?
SVEN SUNGAARD: Yeah, the biggest interesting trend is that we're seeing two peaks develop now in our severe weather season. Traditionally, it's been June. That's been our peak month. It makes sense. It's the early part of summer, still some cool air left to our North, but things are heating up and we get our humidity around here. But now we're starting to see statistically a secondary peak develop in August and September. What that means and what's causing it is a big question mark. We know that September is one of our fastest-warming months due to climate change, so maybe it's that lingering summer that's allowing for a second peak in severe weather around here.
NINA MOINI: Fascinating. Thanks so much, Sven.
SVEN SUNGAARD: You're very welcome, Nina.
NINA MOINI: That's MPR News meteorologist, Sven Sundgaard.
Thanks for being with us, Sven.
SVEN SUNGAARD: Absolutely, Nina.
NINA MOINI: Yeah, this is so important. I don't know if you heard us talking with the Sheriff from Olmsted County earlier in the show, but to already have these tornadoes, how many tornadoes have we had already, and how does it line up to other years?
SVEN SUNGAARD: Yeah, we've had 11 tornado reports so far this April season already. Five of those were just from Friday, two of which were EF2s on Friday. So that's pretty incredible. Minnesota, we tend to see the smaller side of those tornadoes. So those are significant tornadoes, one of which, around Stewartville and Marion, packed 130-mile-an-hour winds and was on the ground for 10 miles. So that's a longer-track tornado. We average only one tornado in the month of April in Minnesota, so that's already way above normal. This is our most active start to the severe weather season in four years.
68 total severe weather reports, which includes large hail and wind, of course, too. And of course, last year was an active season too, but it was pretty brief. Most of last year's tornadoes and activity came just in the month of June. People might remember we had about three weeks there that were pretty bumpy.
NINA MOINI: Yeah. So I think people are wondering like, why is this happening? And does winter weather affect this or the type of winter we had?
SVEN SUNGAARD: Yeah, it can. Severe weather season starts in about February, March in the deep South as things start to warm up there. Spring, of course, gets there earlier and there's still a lot of cold left in the Northern states. And it's that clash of air masses that creates thunderstorms and the potential for severe weather. And this winter was a little odd. People might remember we had some occasional cold, but overall, it was pretty close to average. But we had an unusually strong polar vortex. But it was also very disturbed. We had a lack of Arctic sea ice that helped contribute to that, a La Niña pattern that helped contribute to things.
And so there's been this leftover blobs of cold air. basically, most of Canada and Alaska have seen very cold temperatures March into early April, and so that lingering cold, combined with some pretty hot weather in the South, has created an unusual temperature contrast. You might remember a couple of weeks ago the Southwest seeing record temperatures, so there's plenty of heat and moisture in the Southern part of the country. And we've just been in that collision course. It's finally been migrating North. And so it's been Minnesota and especially Wisconsin's turn.
Southern Wisconsin has had four different episodes of severe weather last week, about double what we've seen. So we think it's crazy here, but it's been even worse to our east.
NINA MOINI: So what does that show, if anything, for spring and summer and how that might go down?
SVEN SUNGAARD: Yeah, so spent a lot of the weekend deep diving into the data, and there really aren't many correlations between April and June. June is our peak month, usually for severe weather, but there isn't much of a correlation there. Typically what happens in Minnesota is we'll get one month that is particularly active, and then the rest of the season is average or even below average. So this might be the one month or maybe June or July could be more active again. But what we have been seeing is that we've been seeing this above-normal precip for April. That was expected.
And whenever we see above-normal precip in the spring and summer months, that usually translates to an uptick in severe weather too. So Climate Prediction Center forecasting equal chances of above or below normal precip and temperatures for May. So it might be a little calmer, but this pattern might linger for another couple of weeks yet.
NINA MOINI: What about trying to assess some of the trends? When you look at the last decade or so, what are you seeing that's shifted?
SVEN SUNGAARD: Yeah, the biggest interesting trend is that we're seeing two peaks develop now in our severe weather season. Traditionally, it's been June. That's been our peak month. It makes sense. It's the early part of summer, still some cool air left to our North, but things are heating up and we get our humidity around here. But now we're starting to see statistically a secondary peak develop in August and September. What that means and what's causing it is a big question mark. We know that September is one of our fastest-warming months due to climate change, so maybe it's that lingering summer that's allowing for a second peak in severe weather around here.
NINA MOINI: Fascinating. Thanks so much, Sven.
SVEN SUNGAARD: You're very welcome, Nina.
NINA MOINI: That's MPR News meteorologist, Sven Sundgaard.
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