Episode 3: Chasing the world's largest tornado

National Geographic Explorer Anton Seimon devised a new, safer way to peer inside tornados and helped solve a long-standing mystery about how they form.

A tornadic supercell thunderstorm, over 80 miles away, with a large tornado touching ground in South Dakota.
Photograph by MIKE THEISS

How do you measure something that destroys everything it touches? That’s an essential question for tornado researchers. After he narrowly escaped the largest twister on record—a two-and-a-half-mile-wide behemoth with 300-mile-an-hour winds—National Geographic Explorer Anton Seimon found a new, safer way to peer inside them and helped solve a long-standing mystery about how they form.


[sound of rain]

ANTON SEIMON [sound from a video recording of a storm chase near El Reno, Oklahoma]: Keep driving hard. Drive us safe—go one and a half miles.

PETER GWIN (HOST): In 2013 Anton Seimon was crisscrossing Oklahoma roads in a minivan. Anton is a scientist who studies tornadoes. And his team saw a huge one out the window.

[Recording: SEIMON: Wait. OK, yeah. Keep going. It’s very close. Got the tornado very close.]

SEIMON: And we began driving south and I thought we were in a very safe position. And then things began to deteriorate in a way that I was not familiar with.

GWIN: All of a sudden, the tornado changed directions. It also ballooned to a much bigger size. Before he knew it, Anton was way too close.

SEIMON: The winds began to get very intense, roaring at us as a headwind from the south, probably blowing at least 100 miles an hour. And as these things happened, we're basically engulfed by this giant circulation of the tornado.

GWIN: Wow.

SEIMON: You know, a four-cylinder minivan doesn't do very well in 100 mile-an-hour headwind. But bless that Dodge Caravan, it got us out of there.

[Recording: SEIMON: All right, we’re probably out of danger, but keep going. Nice going, nice going.]

GWIN: After Anton made it to safety, all he could see was a gigantic wall of rain. In decades of storm chasing, he had never seen a tornado like this.

SEIMON: It was too large to be a tornado. In my head I was trying to understand what I was looking at, but tornadoes are not this large, you know. This is 10 times larger than a large tornado. So how does one get—to get one's head around what's going on. It was really, really strange and weird.

GWIN: It wasn’t just Anton. He was staring at a tornado that measured more than two and a half miles wide, the largest ever recorded. And then he thought of something else.

SEIMON: I said, This is the first storm that's going to kill storm chasers. And I had no doubt about it. It was terrible. You know, it was a horrible feeling.

GWIN: Anton would find out the tornado hit even closer to home than he imagined. He couldn’t bring back the people he lost. But maybe studying the tornado—and learning lessons for the future—could help him find some kind of meaning.

I’m Peter Gwin, and this is Overheard at National Geographic: a show where we eavesdrop on the wild conversations we have at Nat Geo and follow them to the edges of our big, weird, beautiful world. This week: the quest to go inside the most violent storms on Earth, and how a new way of studying tornadoes could teach us to detect them earlier—and hopefully save lives.


GWIN: I’ve always thought of tornadoes as scary monsters. The kind of thing you see in The Wizard of Oz, a black hole that reaches down from the sky and snatches innocent people out of their beds. But that’s not how Anton Seimon sees them. Anton says it all starts with a type of thunderstorm called a supercell.

SEIMON: Where you get a supercell thunderstorm, you have the potential for a significant tornado. Supercell thunderstorms are breathtaking to behold. They're giant sky sculptures. They're extraordinary beasts.

GWIN: And Anton has chased those beasts for almost 30 years. He’s a National Geographic Explorer. And every year, he logs thousands of miles driving around the Great Plains, from Texas to Canada, and from the Rockies all the way to Indiana.

Tell me about the life of a storm chaser. What is that life like?

SEIMON: Yeah, so a storm chasing lifestyle is not a very healthy thing. Typically involves very bad food and sometimes uncomfortable accommodations, ridiculous numbers of hours just sitting in the driver's seat of a car or the passenger seat waiting for something to happen. It's certainly not glamorous.

GWIN: But seeing a storm unfold is worth the wait. Anton says he’s not looking for adrenaline or thrills, just the most promising thunderclouds. And when he finds them, the chase is on.

SEIMON: The analogy I draw is you're playing chess with the atmosphere. And sometimes the clouds never develop. You know, the difference in atmospheric conditions that can produce just a sunny afternoon or a maximum-intensity tornado can be—the difference can be infinitesimally small and impossible to discern beforehand.

GWIN: Even for experts like Anton, it’s a mystery why some supercells create massive tornadoes and others just fizzle out. Tornadoes have killed more than 900 people in the United States since 2010, and understanding them is the first step to saving lives.

Why is it necessary for a person, even a scientist, to get anywhere near a tornado? Isn't that like what radar sort of—isn't technology sort of taking the human element out of this?

SEIMON: What the radar beam does, you know, a radar sends a signal out. It bounces back off particles, objects, cloud droplets, dust, whatever is out there, and bounces back to the radar and gives information.

GWIN: That works great at cloud level. But Anton says there’s one place where things get tricky. At ground level, trees and buildings get in the way of radar beams.

SEIMON: That's where all the structures are, and that's where all human mortality occurs, is right at the surface. So the very place that you would want a radar beam to be giving you the maximum information is that one place that a radar beam can't actually see.

GWIN: So to understand what’s happening at ground level, you have to figure out another way to see inside a tornado. And that’s not easy.

BRANTLEY HARGROVE (JOURNALIST): It's weird to think that, you know, towards the end of the 20th century, we had no data at ground level from inside the core of a violent tornado.

GWIN: This is Brantley Hargrove. He’s a journalist, and he says for a long time we were missing really basic information. Like how fast is the wind at ground level? Is it warm inside a tornado, or cool? According to Brantley, scientists could only guess.

HARGROVE: Structural engineers obviously need to know these things because they need to know, you know, how strong do we need to build this hospital? How strong do we need to build this school? And there were just guesses before this. They were just sort of blank spaces in the equation that nobody had filled in yet.

GWIN: Brantley wrote a biography of Tim Samaras, a self-taught engineer obsessed with filling in those blanks. In the early 2000s, Tim teamed up with Anton Seimon, and Tim built a two-foot-wide probe painted bright orange. It looked like an alien turtle. He designed the probe to lay flat on the ground as a tornado passed over it and measure things like wind speed and atmospheric pressure. Tim and Anton would track a tornado in their car. And then, Brantley says, Tim would grab his probe and pounce.

So walk me through how you put one of those out, like how would Tim deploy one of these?

HARGROVE: So you've got to figure out where this tornado is going to be maybe a minute from now, or two minutes from now, really as little as possible to narrow the margin of error. Then you hop out, you grab that probe, activate it. There's a little switch on the bottom. You lay it on the ground, maybe kind off to the side of the road. And then you hightail it out of there, depending on how close the tornado is.

[Recording: TIM SAMARAS: Oh my god, you’ve got a wedge on the ground.

SEIMON: Wedge on the ground. Wipers, please.]

GWIN: This is video taken in 2003. Anton and Tim are driving around the Texas Panhandle. They pull over. And not far in the distance, a tornado is heading straight toward them.

[Recording: SEIMON: Oh my god, that was—uh, Tim, you’ve got to get out of the car in this. Be careful.]

Tim was so remarkably cool under the pressure there, in that particular instance, when you’re sitting alongside him. I mean, we both were. You know, we are really focused on the task at hand and the safety element. And then baseball-sized hail starts falling down and banging on the roof and threatening to smash all the windows.

[Recording: SAMARAS: All right, how we doing?

SEIMON: You’ve got baseballs falling. Tim, these’ll take your head off, man. Just swing the thing out.]

GWIN: As Anton holds a camcorder in the passenger seat, Tim drops the probe by the side of the road and scrambles back to the car. Then Tim floors it down the highway.

[Recording: SEIMON: You might actually slow down a bit.



SAMARAS: We’re gonna die.

SEIMON: I just don’t want to get broadsided. No, it’s just [unintelligible] wrapping around. Slow down, Tim.

SAMARAS: Oh my god.

SEIMON: Slow down, Tim. Slow down. OK, that’s a hundred miles an hour. Power line down. Left side. Tim, the power poles could come down here. Power poles are bending! I’ve never seen that in my life. They’re bending! Power line’s down. Slow down, slow down.]

GWIN: With 100 mile-an-hour winds knocking power lines right into their path, Tim drives to safety. Anton says just a minute and a half after they fled, the tornado barreled through the exact spot where they pulled over.

SEIMON: When you deliberately cross into that zone where you're getting into that, you know, the path of where the tornado, you know, is going to track and destroy things. It's very strange indeed. And I—yeah, on one hand, you know, every instinct, your body is telling you to panic and get the heck out of there. On the other hand, the scientist in me is just so fascinated by what I'm witnessing.

GWIN: You know, in that video, at one point Tim says, “We're going to die.” And, you know, once you make it out, he says, you know, “That was too close.” I mean, did you feel like that—like you had sort of crossed a line there?

SEIMON: No, I—you hear me sort of trying to reassure Tim. I didn't feel it was nearly as desperate as he was communicating. But yeah, it is very intense, and you know, it was after that particular experience, I evaluated things and decided that I should probably stop trying to deploy probes into tornadoes because if I persisted at that, at some point my luck would run out. Things would catch up with me.

GWIN: After that, Anton stopped chasing tornadoes with Tim. The research was too dangerous, and he wanted to chase on his own terms. Just one month after the narrow escape in Texas, Tim hit it big. He played matador again, this time with a tornado in South Dakota. Journalist Brantley Hargrove says Tim positioned his probe perfectly.

HARGROVE: It hadn't moved an inch, even though an incredibly violent tornado had passed over it. Not only did it survive, he knew it was gathering data. For tornado researchers and storm chasers, this was like the Excalibur moment. I mean, this was like, you know, I've done it!

GWIN: For the first time ever, Tim had collected real, concrete information about the center of a tornado. The data was revolutionary for understanding what happens inside a tornado. And it wasn’t just researchers paying attention. Tim Samaras became the face of storm chasing. He was featured in a National Geographic cover story, and he also starred in a TV show. Tim’s aggressive storm chasing was valuable to scientists and a hit with the public.

HARGROVE: The only way Tim was able to get these measurements was because he was willing to push it a little bit. And so, you know, you push it long enough and eventually, you know, it will bite you.

GWIN: In 2013, a decade after they had last worked together, Tim Samaras and Anton Seimon separately followed the same storm to Oklahoma. Hundreds of other storm chasers were there too. Anton says the brewing storm put a bullseye right on top of Oklahoma City.

SEIMON: So that really freaked me out because, you know, more than a million people are living in that area in harm's way. Also, you know, I've got family members in the Oklahoma City area. I had breakfast with my mother-in-law that morning at a diner, and she said, So how's today looking, you know? And I just implored her. I said, It looks terrifying. I said, If—when those sirens go off later today, get in your basement. Please, just really, this is a bad—this is a really serious setup.

[Recording: SEIMON: All right, are we out—we’re in the edge of the circulation, but the funnel’s behind us.]

GWIN: This is the storm that boggled Anton’s mind—the one that seemed too large to even be a tornado. As it grew stronger, the tornado became more erratic. It chewed through buildings near a small town called El Reno. And it crossed over roads jammed with storm chasers’ cars.

[Recording: SEIMON: All right, that redeveloped very close in on us, people.

UNKNOWN: Love it!

SEIMON: Nice going. So a bunch of chasers were hit by that, no doubt. Anyone behind us would have been hit.]

SEIMON: I freely admit I was clueless as to what was going on. I knew it was strange. I knew that we had to put some distance in there. I thought we were playing it safe and we were still caught.

GWIN: Wow.

SEIMON: So then what about all those people who actually, you know, are trying to be much bolder, trying to get closer in?

GWIN: After the skies cleared, storm chasers checked in with each other. Almost everyone was accounted for. But the next day, no one had heard from Tim Samaras.

SEIMON: And sometime after midnight I woke up, and I checked the social media again. And then for the first time, I saw a note saying, “I hope this rumor's not true, but...” I was like, Oh God.

GWIN: The rumor was that Tim Samaras had died in the tornado. And it was true. The tornado killed eight people, including Tim and his son Paul and another chase partner named Carl Young. According to journalist Brantley Hargrove, the storm changed so quickly that it caught Tim off guard.

HARGROVE: You know, it’s always struck me how unlikely what happened really was. You know, so many things had to go wrong in exact sequence. If they had been 20 seconds ahead on the road or 20 seconds behind, I think they probably would have survived. But they just happened to be in the exact wrong place at the exact wrong time.

GWIN: Anton Seimon and other veteran storm chasers were shocked.

SEIMON: It was just so heartbreaking and so, so sad. And there was this gigantic freakout because there had been no—there’d never been a storm chaser killed while storm chasing, as far as we knew. And so there's a lot of soul searching as, How did this happen? What went wrong? You know, was it the actions of the chasers themselves? Was the storm really that unusual? And in this mystery were the seeds of a major research case.

GWIN: To understand why the El Reno tornado killed his friends, Anton needed to study the storm. And there was a lot to unpack. The tornado was more than two and a half miles wide, the largest ever recorded. Its wind speeds of 300 miles an hour were some of the strongest in weather history. And it created some of the biggest hail recorded anywhere—about the size of volleyballs.

SEIMON: It had these extraordinary phenomena that said, OK, you know, this is obviously a case worth studying. But there's this whole other angle that kind of—as a storm chasing researcher myself—I felt like I really wanted to study the storm to try to understand what the heck happened here.

GWIN: Since the 1990s, an idea had been rolling around Anton’s brain. Maybe he could use video to analyze a tornado at ground level. With so many storm chasers on hand, there must be plenty of video to work with.

SEIMON: I came up with a list of 250 individual chasers or chaser groups who were in the vicinity of El Reno on that afternoon, which is kind of amazing.

GWIN: Yeah.

SEIMON: You know, I had no idea how international storm chasing had become. It turns out there were 30 storm chasers from Australia! They’d come out from Australia to chase American storms.

GWIN: Oh my gosh.

SEIMON: They were all out there surrounding the storm. So things like that were quite amazing.

GWIN: Anton ended up with dozens of videos, a kind of mosaic showing the tornado from all different points of view.

SEIMON: Gathering the material was just the first step. You have to then turn it into scientific data. Now, you know, somebody’s home movie is not instantly scientific data. You have to do all sorts of processing to actually make it worthwhile.

GWIN: This was tedious work. First, Anton needed to know exactly where each video was shot, down to a few feet.

SEIMON: That's now made easy through things like Google Maps and Google Earth. You can simulate scenes and compare what you see on the video to find the perfect match. Even a vehicle driving 60 miles an hour down the road? We know where that camera was.

GWIN: Next, he needed to know when the videos were happening. For this, Anton relied on something that showed up in every video: lightning.

SEIMON: When there are major lightning flashes recorded on video, we can actually go to the archive of lightning flashes from the storm. We know the exact time of those lightning flashes. And we can put together the timeline of all those video clips that we have.

GWIN: Finally, Anton was ready to share his data with the world. He says his videos told the story of the El Reno tornado in a whole new way.

SEIMON: We are able to map out the storm in a manner that had never been done before. We have now an archive of imagery of a single storm over a one-hour period as it goes through the cycle of producing this gigantic tornado and all these other phenomena. You can see it from multiple perspectives and really understand things, how they work.

GWIN: When scientists dug into those videos, they made a huge discovery. Anton published a scientific paper with a timeline of how the tornado formed. And his paper grabbed the attention of another scientist named Jana Houser.

JANA HOUSER (METEOROLOGIST): We collect data through a mobile radar, which in our case basically looks like a big cone-shaped dish on top of a relatively large flatbed pickup truck.

GWIN: Jana is a meteorologist at Ohio University. She had also studied the El Reno tornado, and at first, she focused on what happened in the clouds. Jana worked on a scientific paper that also detailed when the tornado formed. But something was off.

HOUSER: There was actually a two-minute disconnect between their time and our time, with their time being earlier than what we had seen in the radar data.

GWIN: Two minutes. It might not seem like much, but to Jana, this was a major head-scratcher. Why did the tornado show up in Anton’s videos before her radar saw it in the sky? She took a closer look at the data.

Basically you are witnessing the birth of this particular tornado. Is that what's going on?

HOUSER: Yes, that is exactly what is going on. And what we observed with our eyes—that's what Anton's group did—and then what we saw with the radar analysis was that this tornado very clearly started at or very close to the ground and then suddenly expanded upwards.

GWIN: So, picture the first moments of a tornado. Maybe you imagine a scary-looking cloud that starts to rotate. Then a long, black tentacle reaches down from the sky. Even though tornadoes look like that, Jana and Anton realized the El Reno tornado didn’t actually happen that way. The tornado formed first at ground level. Then it spun up to the clouds. Nobody had ever recorded this happening.

HOUSER: From a scientific perspective, it's almost like the missing link, you know. So we have had this theory. We've been able to show this in models, but there has been essentially no or very limited observational evidence to support this.

GWIN: And it wasn’t just the El Reno tornado. Jana discovered that other tornadoes form the very same way. It seems like most tornadoes develop on the ground first. And she says this new information shows a major hole in the way we predict tornadoes.

It all goes back to radar. Forecasters can see what’s happening at cloud level. But on the ground?

HOUSER: We can't actually observe this low-level rotation in 99 percent of the cases, at least using the technology that's available to the weather forecasters at the National Weather Service or even at your local news newsroom.

GWIN: So by the time forecasters detect a tornado and warn people what’s coming, the storm could be a few critical minutes ahead. Anton Seimon says it might be time to rethink how we monitor thunderstorms.

SEIMON: Maybe part of the problem is we've been—we have an overreliance on technologies which are tracking what's going on in that cloud level and not enough focus on what's going on close to the ground, which, of course, you know, what our findings are showing is really where the tornado itself will spin up.

GWIN: Anton wants to fix that. He plans to keep building on the work of Tim Samaras, to find out what’s actually going on inside tornadoes. And maybe his discoveries could even help protect people in the future.

SEIMON: You know, I'd do anything in my power to get my friends back. But given all that has transpired, I feel like we've derived great meaning and great value from this awful experience. And, you know, all these subsequent efforts to understand the storm and for the story to be told as accurately as possible, they're teaching us many things.

GWIN: Anton thinks video data could solve even more tornado mysteries, and his team has become more sophisticated. Now they strategically fan out around a tornado and record videos from several angles. Plus, new video technology means their data is getting better and better all the time.

SEIMON: 4K video is a treasure trove for us because it is so—it's sufficiently high resolution that we can really see a lot of the fine-scale detail—the smaller particles in motion, little patches of dust being whipping around a tornado, leaves in motion, things like that—that really we couldn't see in what we used to consider to be high-definition video. So that's been quite a breakthrough.

GWIN: As Anton closes in on 30 years of tornado research, he still sees a lot of storm chasing in his future.

Even during the Covid-19 pandemic, Anton’s team found a way to chase safely.

SEIMON: We did some unusual things. We brought 10 days of food with us. And so we never actually had to sit down in a restaurant anywhere. You know, actions like that really helped. But the key was always being vigilant, never forgetting that this is an unusual situation.

GWIN: What is it that pulls you out every spring? I mean, like you said, it seems like you’ve seen it kind of all, from El Reno on down.

SEIMON: One of the most compelling things is that—you said you must’ve seen it all is we absolutely know we haven't seen it all. And that draws us back every year because there's always something. Every year brings some new experiences. And if I didn't have a research interest in the world, I'd still be out there every day I could.

GWIN: When big storms start thundering across the Great Plains in the spring, Anton will be there. And his video camera will be rolling.

More after the break.

GWIN: There’s something about tornadoes that’s completely mesmerizing. You just can’t look away. And you can see that for yourself in our show notes. We have links to some of Anton’s tornado videos.

You can also find out more about tornado science. We have cool graphics and videos that explain how tornadoes form and some helpful tips to stay safe. There’s even a list of emergency supplies to stock up on, just in case.

And for subscribers, you can read a National Geographic magazine article called “The Last Chase.” It details why Tim Samaras pushed himself to become one of the world’s most successful tornado researchers, and how the El Reno tornado became the first to kill storm chasers.

That’s in the show notes, right there in your podcast app.


Overheard at National Geographic is produced by Jacob Pinter, Brian Gutierrez, and Laura Sim.

Our senior editor is Eli Chen.

Executive producer of audio is Davar Ardalan, who also edited this episode.

Our fact-checker is Michelle Harris.

Hansdale Hsu composed our theme music and engineers our episodes.

This podcast is a production of National Geographic Partners.

Whitney Johnson is the director of visuals and immersive experiences.

Susan Goldberg is National Geographic’s editorial director.

And I’m your host, Peter Gwin. See y’all next time.


Want more?

See some of Anton’s mesmerizing tornado videos and his analysis of the El Reno tornado.

Check out what we know about the science of tornadoes and tips to stay safe if you’re in a tornado’s path.

Plus, learn more about The Man Who Caught the Storm, Brantley Hargrove’s biography of Tim Samaras.

And for paid subscribers:

Read “The Last Chase,” the National Geographic cover story chronicling Tim Samaras’ pursuit of the El Reno tornado.