Is tornado activity increasing in Minnesota?

Tornado damage
Residents navigate through fallen trees on Sheridan Avenue Monday, May 23, 2011 after a tornado ripped through Minneapolis, Minn. Sunday.
MPR Photo/Jeffrey Thompson

The tornados over the weekend in Minneapolis, Wisconsin and Missouri are the latest in what seems to be a busy spring for twisters.

Meteorologist Paul Huttner and University of Minnesota geography professor Kenny Blumenfeld discussed the increase in tornados and whether urban residents should expect more tornados in the near future with Morning Edition host Cathy Wurzer on Tuesday.

View photo galleries of damage from the tornado and the ensuing cleanup.

Blumenfeld, a nationally recognized expert on urban tornados, said a significant tornado hits the Twin Cities every 10 to 15 years. "So I would expect something fairly significant at some point in the future," he said.

An edited transcript of their conversation is below.

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Cathy Wurzer: Paul Huttner, I'm going to start with you first. I'm thinking about Tuscaloosa, Joplin, these were monster storms, and as you know, they're on top of a record number of tornados in Minnesota last season. Do you think there's some kind of atmospheric change that's fueling this wild weather?

Paul Huttner: Well, I don't know, but I do know that it is persistent. It's like somebody flipped a switch, certainly starting for Minnesota last June 17th. And the active weather just has not stopped since then.

We're already up to 1,162 tornados or so in the United States so far this year. The average to date (is) about 671. We had 55 Sunday. We had 11 Monday. We're almost at our three year running average for tornados for the whole year right now, which is a little over 1,300. So it's been incredibly active, and it doesn't seem to be stopping.

Wurzer: : Professor, do you have a theory at all?

Kenny Blumenfeld: No, I agree completely with Paul. It's a very active pattern, and when you have a strong jet stream and a lot of moisture flowing into the systems that the jet stream is helping to create you have the ingredients that are needed, and it's very persistent. In fact, today it looks like another very big day, and then tomorrow, too.

Wurzer: : Down in the southern areas.

Blumenfeld: Down to the south, yes.

Wurzer: Forty-eight people were injured in north Minneapolis. One man died as a direct result of his injuries. The last time we had that many injuries was back in 1981 with a twister that went from Edina to Roseville. I'm curious, Paul, what do you think is behind the relatively high number of injuries in this latest storm, even with better warning systems? Is there warning fatigue?

Huttner: Who knows, Cathy. It went through a densely populated urban area, and you're going to have a higher number of people beneath the path of that tornado. I think some of that is just the luck of the draw. It's bound to happen when you put an EF2 tornado right through a metropolitan area as we had on Sunday.

Wurzer: Which leads me then to Kenny Blumenfeld because we had a quote from a lady who said she didn't think tornados could hit a city. So she was surprised to look out her window to see this twister. Is this still a pretty common misconception?

Blumenfeld: Apparently. People seem to believe that tornados, because they appear to be everywhere else, they can't hit where they are. And that's patently false. If the ingredients are right, a tornado can hit just about anything, and cities are no exception.

We've had since 1990 over 300 tornados in cities with populations of over 100,000 people, and those tornados by and large have done damage and about 15 percent of them have actually caused significant injuries and even fatalities.

Wurzer: There have been a couple of tornado hits in Minneapolis, not only obviously this year, but in the past couple of years. Is it a matter of time before we see another big one come through the metro? It's obviously hard to predict. I understand that, but with urban sprawl and that kind of thing going on, Kenny?

Blumenfeld: Well, I think that it's certainly a matter of time. I don't think we need to be in panic mode, but it's clear that if you look at the history, we've had strong and significant tornados throughout the history of the Twin Cities area, every 10, 15 years or so, you get something pretty big. So I would expect something fairly significant at some point in the future, yes.

Wurzer: Quick word, Paul Huttner?

Huttner: I agree with Kenny completely. He's crunched a lot of the numbers on urban tornados, and it is bound to happen again. We've had a lot of urban tornados in the last year, as you've pointed out, Cathy. And you know why? Maybe La Nina. La Nina is typically active with the jet stream, warm waters in the Gulf of Mexico. A big temperature contrast just seems to be fueling the storms this year.

(Interview edited and transcribed by MPR reporter Madeleine Baran)