The Tornado Science To Know Before Seeing ‘Twisters’

RACHEL FELTMAN: This is Science Friday. I’m Rachel Feltman. The movie Twisters, the long awaited follow-up to the 1996 movie Twister, drops in theaters today. It’s about a tornado scientist who goes back to her home state to try and stop a massive tornado outbreak. On the way, she meets a quirky cast of characters who are mega enthusiastic about tornado science.

SPEAKER 1: You thought you could destroy a tornado.

SPEAKER 2: We never had a chance.

[DRAMATIC MUSIC]

SPEAKER 1: You want one?

RACHEL FELTMAN: The movie is definitely fun, thrilling, and features a love story, but it also shows the ways that tornadoes can affect people’s lives in the real world. This premiere comes after an unusual and powerful peak tornado season in the Midwest, according to experts, with additional tornadoes touching down in Chicago and upstate New York this week, killing at least one person.

But just how tornadoes will continue to change is something we still don’t know. SciFri digital producer Emma Gomez saw the movie and spoke to a meteorology expert to decode some of the science from Twisters and talk about how real-life tornadoes are changing.

EMMA GOMEZ: Joining me is Dr. Bill Gallus, a meteorology professor at Iowa State University. Welcome to Science Friday, Dr. Gallus.

BILL GALLUS: Well, hello, Emma. It’s nice to be here.

EMMA GOMEZ: So, before we start, could you just give us, like, a brief elevator pitch about what it is that you study?

BILL GALLUS: I study thunderstorm systems in general and ways to try to improve the forecasts. I also have an avid interest in severe weather, so I do some research related to tornadoes, assisting engineers in the development of large tornado simulators, so we can understand how they impact structures and hopefully, within a decade or two, find better ways to build structures to withstand more tornadoes.

EMMA GOMEZ: So you study tornadoes, but I’ve heard that you also been storm chasing, and you’ve even taken your students on storm chasing trips. That’s not your average field trip, right? So, what are those like?

BILL GALLUS: So I have chased tornadoes for 37 years, but this is the first year at Iowa State. We developed a course called Field Observations of Thunderstorms, and part of the course was an eight-day field trip where we took 13 students out across the Central United States for this eight-day period in late May.

And we actually got very lucky because this was probably the most active eight-day period that the United States has seen for severe weather in many years. So it was quite the experience. And I felt very good for the students because we did get to see tornadoes on three of the eight days.

EMMA GOMEZ: Wow. That is super interesting. And so, Twisters, the movie, there’s a lot of storm chasing in that. And you just saw that movie. What did you think of it?

BILL GALLUS: I have to say, technology available to storm chasers has improved immensely since the first Twister movie in 1995. And likewise, it’s obvious when you see this new movie that the technology available to Hollywood to recreate, very accurately, the skies, the thunderstorm structure, and the various shapes and colors within tornadoes has also improved drastically. So I thought it was quite the thrill ride because it was so realistic in terms of how it portrays the actual weather conditions.

EMMA GOMEZ: Right. And did you see it in 4D? Am I right there? [LAUGHS]

BILL GALLUS: Yes, I did not know that until I arrived at the theater. And I had never seen a movie that way. And I have to say, if there is a movie to see in 4D, this is the one.

EMMA GOMEZ: Wow. [LAUGHS] OK. So, I mean, when I saw the movie, speaking from the perspective of somebody who’s not a tornado or severe weather expert, I thought that it took a super information-heavy approach to tornado science. There was just a lot of jargon in it that I really need you to help me understand. So are you game to talk about that?

BILL GALLUS: Yes. In fact, as a scientist, I love to hear what you just said. And they did an excellent job of getting the science correct in this movie.

EMMA GOMEZ: Amazing. OK, so let’s start with a basic one. They use something called an EF scale in the movie to determine the severity of tornadoes. They talk about that a lot. So what is the EF scale, and how does it work?

BILL GALLUS: So everybody wants to know how strong a tornado is, but unfortunately, they’re so violent and full of debris that even if they did hit a weather instrument, they would likely destroy it. So we really never get measurements of the actual winds in tornadoes, which forces us, instead, to rate them based on the damage that they do.

For many decades, we had used a scale developed by Fujita, which was known as the F scale. In the late 2000s, there were modifications made to the scale to provide, really, more accurate rating across the country. And this is called the Enhanced Fujita Scale, or the EF scale. And it still goes from 0 to 5, like the old Fujita scale did.

EMMA GOMEZ: OK, got you. So an EF 0 is like a weak, low speed, and then EF 5 is the most severe?

BILL GALLUS: Yes, you have that exactly right.

EMMA GOMEZ: OK. So, when the characters are describing the conditions for tornadoes in the movie, they use a lot of words like “wind shear,” “updraft,” “mesocyclone,” things that I was kind of googling after I saw the movie. Can you describe the ingredients that make up a tornado and maybe define some of those words for us along the way?

BILL GALLUS: Right, so tornadoes come from thunderstorms, but tornadoes also need another key ingredient, which we call wind shear. And all wind shear means is that the wind directions or the wind speeds, or both, are changing as you go up in the atmosphere.

And why wind shear is important is it gives you a rolling motion in the atmosphere that you can actually see for yourself, if you put a pencil in one of your hands. Lay it in that hand, and you’ll notice that as you take your top hand and move it along the top of the pencil, the pencil rolls. So that is why wind shear is important, because when you have the thunderstorm updraft, it’s as though it is taking one end of the pencil and tilting it upward. And you’ll find that now you have the same kind of rotation that we see in tornadoes.

Also, the updraft in the thunderstorm leads to the ice skater effect. If you’ve ever watched a figure skating performance, at the end, the skaters usually want to end with a bang, with a nice finale, and so that they bring their arms in, and they spin much more quickly. This is what is happening, then, in the thunderstorm. As the air is rushing into the storm at low levels, it takes that rotation, and it can really concentrate it, which helps us to get a tornado.

EMMA GOMEZ: Oh, wow, OK. I love the pencil analogy. That makes a lot of sense to me. So, we’ll move on to one of my favorite moments in the movie, which was when one of the characters sees two tornadoes at the same time, and he yells–

SPEAKER 3: We got twins! Twins!

EMMA GOMEZ: So is that something that actually happens?

BILL GALLUS: It does happen. And it is rare enough that the screaming that you heard, I have to admit, I did the same thing last year when I ended up in a similar situation. I think most storm chasers get extremely excited if they see two on the ground at the same time because it is rather rare.

EMMA GOMEZ: That’s great. So, the National Weather Service confirmed that there were at least 11 tornadoes during Monday night’s storms in the Chicago area. How do groups of multiple tornadoes come about like this?

BILL GALLUS: So there are different ways that that can happen. You can have a family of tornadoes, many tornadoes from multiple storms close together. You can even have one rotating thunderstorm. We call it cyclic tornadogenesis. So you’re producing one tornado for several minutes. It lifts. Another tornado touches down very soon after. So you can get a lot of tornadoes from the same storm.

And the Chicago event was very interesting because those tornadoes came from a line of thunderstorms. And when the conditions are right, a system like the one that affected Chicago can produce many different tornadoes fairly close together all at the same time. They tend to not be as violent, as intense as if they were coming out of a rotating thunderstorm by itself. But as we all saw this week, they can still do a lot of pretty significant damage.

EMMA GOMEZ: Yeah, definitely. And I’ve been seeing some reporting about how the places where tornadoes are likely to hit are shifting or that tornadoes are clustering into these groups when they hit. Is climate change to blame for these shifts, or what do we know about why this is happening?

BILL GALLUS: Everybody always wants to know how climate change is impacting different weather extremes, and that can be very challenging. That’s also true for tornadoes because the warming climate is supplying more instability, which, of course, is something tornadoes want, but it also tends to weaken wind shear, at least in a global sense, across the planet, which would reduce the chances of tornadoes.

We have noticed in the last 10 or 20 years that we seem to have these bigger gaps where the United States gets very quiet, and then periods with a lot of action. And this year, for instance, has been extremely active, the second most active year after 2011. But we’ve had a lot of very quiet tornado years as well.

So we are noticing that it seems tornadoes are happening on fewer days. But on the days where we maybe do get enough wind shear, because we have more energy, we’re seeing more tornadoes tend to touch down. So the tornadoes are getting concentrated into fewer days, which means, in the net, you can’t say that climate change is causing more tornadoes. It’s just changing the distribution of the tornadoes that we see.

EMMA GOMEZ: And so, I mean, in the movie, they throw chemicals into a tornado to try and stop it in its tracks. I don’t know what you think of, you know, that idea, but how do scientists think about minimizing the risks tornadoes pose to the public in real life?

BILL GALLUS: So I felt that the movie did an excellent job on the science. The one thing that maybe it was ahead of its time, I should say, is I am not aware of any researchers trying to find ways to actually dissipate tornadoes. So what we instead try to do is improve our ability to forecast them and to give warning to people so that we can save more lives that way. But at the moment, I think our attitude is, we’re stuck with them.

I thought the movie did a good job of showing how dangerous they actually are and the really terrible impacts they have on people. The movie did not shy away from having the tornadoes caused damage and injury and death.

In addition, we scientists have a very difficult time getting the information we need about what the winds are doing in or very close to a tornado. And one of the reasons is it is, indeed, very dangerous. And so I thought the movie conveys that even for the experts, the storm chasers, there is a lot of danger when you get close to a tornado.

EMMA GOMEZ: Well, that is all the time we have for now. I just want to say thank you so much for taking the time to talk with us and for braving the storm in 4D on our behalf. [LAUGHS]

BILL GALLUS: Well, thanks, Emma. That was easy to do.

EMMA GOMEZ: Well, that is Dr. Bill Gallus, meteorology professor at Iowa State University.

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