Tornado Alley is Shifting Eastward—and We’re Not Ready

Season 1 • Episode 4

Tornadoes are nasty and dangerous. They appear and disappear so fast, there’s usually no time for evacuation—and the United States gets 75% of all the world’s tornadoes, about 1,300 of them a year. They occur all year ‘round, in all 50 states, but the biggest swarm forms in Tornado Alley, in the southern Plains states like Texas, Oklahoma, Kansas, and Nebraska. In 2018, storm chaser and meteorologist Victor Gensini made a startling discovery: Tornado Alley has been shifting eastward. Their growing frequency in Mississippi, Alabama, and Tennessee is a deadly development, because more people live in these areas, often in flimsy housing. And because there are more trees and buildings, it’s much harder to see the devastation coming. 

Guest: Victor Gensini, storm chaser and meteorology professor at Northern Illinois University.

Episode transcript


Theme begins.

In the climate-change era, the disasters you hear about most often are wildfires and hurricanes. And droughts. OK, and flooding. Tornadoes don’t get as much love. But maybe they should.

Victor I think they’re the sexiest of all hazards. 

Victor Gensini is a meteorologist and professor, but above all, a storm chaser. And in 2018, he published a paper that freaked out a lot of people.

Victor Everyone was up in arms, and I had like 500 media requests overnight. 

I’m David Pogue, and this is “Unsung Science.”


Season 1 Episode 4: Tornado Alley is shifting eastward, and we’re not ready

The United States gets 75% of all the world’s tornadoes—about 1300 of them a year. But I’ve never seen one live, and the odds are pretty good that you haven’t either. So when you ask most people to picture a tornado, they picture scenes from tornado movies.

Victor If you’ve never seen a tornado before, your perception of tornadoes was created by Hollywood. And if you look at all the movie covers, “Twister” included, they all have this elephant trunk, high-visible tornado doing damage, people running away from it. Right? A very slender elephant trunk style tornado, high contrast, very visible.

Meet Victor Gensini. He’s a professor of meteorology at Northern Illinois University.

Victor In reality, you can see tornadoes that are miles wide. They’re hard to distinguish what’s cloud based, what’s the surface. They’re very low-contrast. Sometimes they’re happening at night. Sometimes they’re happening downtown Atlanta, Georgia. There are nothing like this beautiful, majestic, just-moving-through-a-wheat-field, “Wizard of Oz” tornado. 

[FILM CLIP Wizard of Oz: “It’s a twister, it’s a twister!”

Gensini may identify as a college professor. But he only got into teaching because the job would accommodate his first love…

Victor The major event that got me into meteorology was when a tornado hit my high school. And I was on a path for engineering and then, like, put the brakes on real quick the next day and said, “Nope, nope, nope, I need to find out more about this atmospheric science stuff.” 

And then, you start to poke around what careers are out there, right? Forecaster, broadcast television meteorologists, so on and so forth. And the professor gig is great, because I get to share my love of meteorology with students. But most importantly, I get to perform whatever kind of research that I think is important to help move our field forward. 

And by “research,” what he means is—

Victor I storm chase. I drive 10 to 20,000 miles every year across the Great Plains looking for these storms. I don’t like to see destruction. I like to watch storms.

I love the landscape. I love the people. Lots of those areas, you know, are—they’ve been untouched since the Homestead Act in the 1930s. I mean, you drive through towns like Boise City, Oklahoma, that still look like, you know, they are a relic of the Dust Bowl in the 1930s. 

David Are you able to describe verbally what these storms sound like when you’re chasing? 

Victor A lot of people say a freight train like, you know, this huge truck driving through my living room. To me, the best analogy that I can give you is standing in front of a massive waterfall like Niagara Falls in that whooshing sound that you hear, almost a—[blowing noises]. 

David Is it a lot of sitting around? I mean, you can’t schedule this. 

Victor Oh. Oh, my gosh. People don’t understand what storm chasing is. Storm chasing is 99.9% driving in a vehicle. So you got to be around people that can make conversation, make you laugh. You get along, you tell stories, you listen to music, right? 

And then that—you know, that tiny point one percent is what you go for, you know. And sometimes they’re great storms, but they don’t produce tornadoes. We’re just looking for the majestic supercells, the beautiful pictures that you see sort of behind me on the wall, right? 

I mean, obviously, this is a podcast, so you can’t see what he’s talking about; I was talking to him on a Zoom call. But they were blowups of stunning supercells: these massive, MASSIVE cylindrical cloud formations, towering up to the heavens. 

Victor Those, those are what we care about. When you get to see things like tornadoes, it’s just kind of icing on the cake. 

And, you know, there’s always something to photograph. Even if it’s not a beautiful tornado in a wheat field, there are still things—skyscapes, sunsets, lightning storms, you know. Old ‘56 Chevies laying in the middle of a field, right, that are rusted out—and there’s always kind of cool landscapes to take in, and that’s I think what all of us are in it for the most, is just to be out there with nature. 

David Oh, so you’re not tornado chasing—you are just storm chasing. 

Victor That’s the key. I think people don’t know the difference, right?  I’m really out there just to see thunderstorms. I love photographing. And, you know, it makes me a better scientist because I get to visually see these storms up close versus trying to model them inside of a computer. It makes me certainly a better forecaster, a better researcher. 

Now, it was news to me that storm chasers aren’t really tornado chasers. I mean, that’s definitely not the impression you get from watching “Twister,” the 1996 movie about storm chasers. 

[Twister movie clip]

ACTOR: I got it! Let’s go, move!…Debris! We have debris!

Yep, that was the tornado movie with the flying livestock.

HUNT: Cow!

COW: Moo.

HUNT: Another cow!

BILL: Actually, I think that was the same one.

Victor I think scientifically, you know, those movies are generally very inaccurate. I think they’re good in that they spark interest in STEM fields in general. I know a lot of people at atmospheric science that got interested in meteorology from the movie “Twister,” despite all of its fallacies and so on. But, you know, they’re not peer-reviewed.They’re not science, they’re just entertainment. They’re just Hollywood. 

David Yeah, well, I wanted to run a line from Twister by you that is made to sound like pseudoscientific jargon. 

Victor Sure. 

David So Helen Hunt says: 

Hunt [from the movie“Twister”]: “Looks like the dry line has stalled. Give me a sector scan west, northwest, look at mid-levels for rotation and increase the PRF.”

Victor I love that line. There’s some credibility to that. If the dry line has stalled, there’s probably strong convergence along the dry line, which means that storms are likely initiating. So when she says ‘west, northwest,’ that would be a preferred area if you were a storm chaser. 

David And how about ‘increase the PRF’?

Victor Oh, yeah, ‘increase the PRF’ would be the pulse range. You’re increasing the amount of the pulses that are being sent out by the radar. 

I think Jan de Bont went to, right, those, those scientific writers and said, “if I were a storm chaser, you know, what would I say if I was all excited about storms developing?”  

David Wow. What do you do when you go storm chasing? 

Victor I do some scientific measurements, right? I will launch weather balloons. We’ll take measurements of the near surface and upper level pressure, temperature, dew point, wind speed, right, all these all these variables that meteorologists care about. But we’re at a very, very safe distance from the storm. And even when I’m actually chasing, trying to get, quote unquote, close, I don’t get into what’s called the bear—bear’s cage of the storm, or in fact, I think Dusty—Seymour Hoffman, in that movie, right, talks about it. “They’re in the Bear’s cage! You could really feel it with a telephoto lens,” right? 

[Bear’s cage “Twister” clip]

Hoffman They’re in the Bear’s cage! Take a peek! You Can really feel it with a telephoto lens!

Melissa No!

Just a side note here: I can’t tell you how much I love that Victor Gensini has the dialogue from “Twister” memorized. Anyway, going on… 

Victor We’re never that close. It’s really scientifically uninteresting when you’re up in there in the tornado, because you can’t see anything! There’s so much rain and dust swirling. The real—the real beauty, honestly, is, you know, several miles away from the storm, kind of taking in the entire, you know, majestic skyscape that these supercells can produce. 

David It seems like in the climate change era, all we hear about is hurricanes, hurricanes, hurricanes. Do you consider tornadoes underappreciated? 

Victor I think they’re the sexiest of all hazards. I think the appeal of the tornado is its short lifespan. It comes and goes very quickly, versus a hurricane. In addition, the damage right after tornadoes is often a little bit more impressive than hurricane damage.

I mean, I’ve seen tornadoes remove homes from foundation and put them in the neighbor’s yard. I’ve seen a smart car thrown three hundred and fifty yards, smashed up like a soda can, vehicles flipped over, roofs torn off, right, houses, well-built homes completely removed from the foundation. And the only thing that is remaining are bolts that are being pulled out of the concrete. 

I mean, so these are—you talk about forces that are required to do that. Remarkable, remarkable forces that must be required to do that. 

David I mean, hurricanes and tornadoes are both huge rotating masses of air. Right? 

Victor Yeah, hurricanes are different in that they’re much, much larger than tornadoes. I mean, tornadoes, many of them are a couple hundred yards wide, okay? They last for maybe on the order of minutes, if you’re lucky. 

Hurricanes are things that last days, sometimes weeks, and they have tropical origin to them.

But at the end of the day, they’re both doing the same thing. The thunderstorm and tornado itself is an energy transfer mechanism. It’s trying to take stored, pent-up energy, heat and humidity near the surface, and transport aloft. The hurricane is trying to do the same thing. 

At the end of the day, extreme weather is just an energy transfer mechanism. And that’s—that’s the idea of climate change, right, is that these storms are getting more intense because there’s more of an energy imbalance where the temperatures are warmer, right? 

David Why is it that the United States leads the world in tornadoes? 

Victor It’s our geography. We have a north-south oriented mountain chain to our west, the Rocky Mountains—that’s generally where you’ll see a hotspot of tornado activity just downwind. They do happen other places. But U.S. is very, very unique because we have that north-south oriented mountain chain. But we also have easy access to humidity, moisture, and that’s the Gulf of Mexico. 


You know…I’ve interviewed a loooooooot of scientists over the years. And one thing I’ve noticed is that the ones who teach…are often really good explainers. Because they’ve had so much practice. 

Check out how Victor Gensini describes how tornadoes form—with analogies to common household appliances.

Victor If it’s a really, really cold summer day and you open the freezer, what happens to that air as it comes out? It comes out immediately, sinks to the ground. It’s very cold and dense.

On the other hand, hot air always wants to go up. As Victor points out,

Victor You never talk about a cold air balloon. You only talk about a hot air balloon. You get that air hot. It’s less dense, it’s buoyant. It wants to rise. 

OK, so cold air wants to sink down. Hot air wants to rise. But in the middle of the U.S., those layers start out reversed. The cold, dry air is up high, coming off of the Rocky mountains. The warm wet air is down low, coming off the Gulf of Mexico.

Victor So when you have cold air aloft and warm air at the surface, they essentially just want to trade places, right? 

If you take your index fingers and put them right in front of your nose, create some rotation that looks like it’s going forward in front of your nose. 

If you’re doing this right, your fingers are pointing toward each other, doing a sort of “Keep rolling!” motion. Oh, but P.S.— if you’re listening to this while you’re driving, keep your damn hands on the wheel.

Victor Keep that rotation going, and then point your fingers towards the ceiling. Okay, so what happens is you take that horizontal spin in front of your nose and as your fingers point towards the ceiling, it becomes spin, but now it’s along a vertical axis. And it’s that spin along the vertical axis that can create these mesocyclone, the rotation inside of these parent storms. 

David Okay, how does that log lying down, that column of air that’s lying down, rotate 90 degrees so it’s pointing up?

Victor You’ve got to have a strong updraft to push it up. So imagine again, your fingers push up that updraft, that updraft is pushing up that rotation into the vertical. 

OK. So now you know how tornadoes form, why the U.S. is the global leader in tornadoes, and how they’re different from hurricanes—tornadoes are much smaller, and they come and go in a matter of minutes. And they can do much worse damage.

Now we come to Victor Gensini’s paper, the one that generated 500 requests for interviews.

Victor The idea for the study actually just became—I was, we were, again, I mentioned I storm chase. We had a couple years in a row, I think it was like ‘12, ‘13 and ‘14, just really abysmal tornado years. I mean, very good for the people of the Great Plains, very bad for me. Very bad. 

And I was like, over the last good record that we have—have there been any spatial trends? 

And so I started just, you know, throwing numbers into spreadsheets, looking at various regions, how the trends happened in the regions. And I remember—I distinctly remember sitting at my computer and I hit Enter. I was like, “wow, that’s fascinating.” And I knew right away I was like, this has to be published immediately. I think that the next morning I started writing the paper immediately.

After the break—I’ll tell you what he discovered. Yeah, I know, that’s super manipulative, making you wait through the ad break. But hey—how much did you pay for this podcast?


Before the break, I left you tantalized and tormented by the promise that I would reveal the contents of Victor Gensini’s discovery about American tornadoes. 

Victor I think I wrote the paper and maybe three or four days with Harold Brooks. We got it submitted. And actually, funny story—the first place we went to it was the Bulletin of the American Meterological Society. We were actually rejected there. But it eventually got to the peer review literature in Nature—probably a higher-impact journal anyway. 

And what the paper said was that Tornado Alley is moving. It’s shifting to the east, from the wide open, unpopulated Plains states into the more densely populated states where a lot more people can die.

Although to be fair, Victor hates the wording I just used.

David All right. So we Americans may have heard of Tornado Alley. What is that? 

Victor It’s a term I don’t like. 

David Really! 

Victor I don’t like it, I don’t like it, it’s a media misconception, right? 

If I tell you Tornado Alley, first of all, most people are going to imagine themselves in Kansas or Oklahoma or Texas. 

The answer is, Tornado Alley is everywhere. Tornadoes happen in all 50 states, including in Alaska and Hawaii. Yes, they happen with higher frequency in Texas, and Oklahoma, and Kansas, Nebraska. 

It just, it leads people to believe that if I’m in Ohio or I’m in North Carolina, I don’t have to worry about that. Tornadoes, again, can happen any time of the year, as long as those conditions are favorable. And so, you know, I’m kind of getting away from the use of ‘Alley,’ even though there is certainly an area of the country in the central Great Plains. 

David Well, what should we call it? The ‘greater frequency zone’? 

Victor Yeah, that’s a good question. ‘The tornado high frequency zone.’ I don’t know. I don’t have a good name for it. You know, I think I’m okay with the use as long as everything that I just said is also said alongside of the use of “Tornado Alley,” so that we educate people that the alley is not just an alley that has hard bounds. 

He’s got an issue with “alley” part of “tornado alley.”

Victor First of all, what do you think of when you think of alley? You think of bowling alley, which means there’s a lane.

David When I was researching this, most of the scientifically-based maps that I saw showed, yes, a higher concentration in Texas, Oklahoma, Kansas. But it was it was not, as you say, a strip. It was like this giant amoeba. 

Victor It almost looks like—a C. The top of the C starts in like Illinois, Indiana. It arcs out towards Iowa and Nebraska. It comes down through the central plains of Texas, Oklahoma. And then it actually curves back towards Alabama and Mississippi and even portions of Georgia. So there’s it’s like a C-shape, where Missouri is kind of cut out a little bit. 

What’s interesting, though, David, is if you plot the number of tornadoes, but then plot the number of tornadoes that kill people, there is a huge dichotomy there. Tornadoes happen in the plains, but where are they killing people? Totally different. I mean, we’re talking hundreds of miles east from the greatest frequency zone where people are dying. 

David And this is where your paper comes in. Right? 

Victor Yeah, absolutely. What we’ve been seeing over the last 40 years is Kansas, Oklahoma, Texas, et cetera.—these Great Plains, the Tornado Alley, if you will, even though I hate that term—decreasing there, right, with frequency. So over the last 40 years, the number of tornadoes that we’ve seen there have actually gone down. 

And where they’ve been increasing in places like Mississippi, Alabama, Tennessee, portions of the mid-South. And in those areas, there’s lots of trees. If you have lots of trees, it’s very hard to see the incoming storm and incoming tornado. Storms there are more likely to happen at night because of their basically distance away from that north-south oriented mountain chain, right? So when they’re happening, right, it’s more likely they’re moving east into the overnight hours. 


And the reason we care about nighttime arrivals is the same reason we care about trees: If you can’t see the tornadoes coming, you’re not as prepared—and you’re more likely to die.

But wait—it gets better. Meaning worse.

Victor But probably most importantly is we have a more vulnerable population. You have a lot of people in the south, mid-south, living in a weak frame housing stock and mobile homes. I mean, some counties in the mid-south, upwards of 80, 90 percent of their infrastructure that people are living in, residential, is mobile homes. And we know if there’s one place you don’t want to be in a mobile home—or during a tornado, it’s in a mobile home or in a vehicle, okay? 

Just because of this issue, they’re more likely to produce casualties. 

David So what you confirmed is that—let me see if I phrase this right. The amorphous, roughly C-shaped amoeba of higher probability traditionally associated with the Plains states is shifting eastward into more populous, more vulnerable states. 

Victor Almost correct. I love the description, except I would not use the word shift. 

David But, but, but, but even the word ‘shift,’ though, could just mean a shift in preponderance, or a shift in likelihood. 

Victor Exactly. If you’re talking about a shift in the probability space, that’s exactly what it is. If you’re talking about a geographic location shift, that’s where the issue comes in. 

We don’t want to tell people in Oklahoma and Texas they don’t worry about it, it’s shifting. What we really want to highlight is this increasing threat from tornadoes, greater frequency, greater number—happening in the mid-south, where we know people are already extremely vulnerable due to socioeconomic issues. 

David Okay, so—in Tornado Alley, still the most tornadoes, still a lot of tornadoes. 

Victor Yes. 

David And farther east, an increasing number of tornadoes. 

Victor Exactly. Exactly. 

David And why?

Victor It’s very likely to me that it’s a component of the actual input into the atmosphere from humans. So anthropogenic climate change, in addition to some degree of natural variability. 

Victor It’s very consistent with what our climate models show as we get into later this century, where the Great Plains, specifically Texas, Oklahoma, begin to dry out and become basically these big heat domes, hot heat domes, that don’t produce a lot of severe weather. 


And so, in October 2018, Victor’s paper appeared in the journal Nature. It raised a lot of eyebrows, and dropped a lot of jaws.

Victor The, the trends study obviously garnered a lot of public attention. A lot of the Associated Press, a lot of the news articles were like, ‘Tornado Alley is shifting, ahhh!’ Right, and everyone was up in arms, and I had like 500 media requests overnight. 

I mean, there’s lots and lots of issues and caveats, as there are with almost any scientific study. So it’s, it’s my—I felt it as the lead author, I sort of took it upon myself that, you know, I’m going to do as many of these interviews as I can. I want to sort of set the record straight in terms of what we know and what we don’t know about things like tornadoes, tornadoes and climate change. 

David Okay, so—is real life bearing out what you said? Are Tennessee and Mississippi, are they seeing more damage, more loss of life? 

Victor Absolutely. I mean, if you look at the data from ‘19-’20, and then the preliminary data so far from ‘21, very active in the southeastern United States. 

After we published that study, for example the Nashville tornado occurred. I don’t know if you remember that event as well. 

I do remember it. It was March 2020.

[News clip montage]

BRANDIS We heard the wind and got the alarms on our phones. And we just sprinted out of the building. So running down the hallway, the ceiling was just caving in, debris everywhere, and water is pouring from the ceiling, like waterfalls in the hallway. 

GUY The whole back of the roof was caved in, the front of it caved in, we have no front porch, and all the houses down our street are completely gone.

NEWS If you look in the distance, that is the cone, or the V of the tornado as it was actually touched down in Nashville. This is a massive, massive funnel on the ground right there. You can see just how big that is, which is why we’re seeing this type of damage over a wide area.

In the end, the Nashville tornado killed 25 people and cost $1.6 billion in damage—the sixth costliest tornado in U.S. history. And it was hundreds of miles east of the traditional Tornado Alley.

Victor So there are a lot—I hate to cherry pick just Nashville, but there are events that have continued to occur and will continue to occur in the southeastern United States. 

Victor says that the climate crisis isn’t the only reason the death and destruction are getting worse. We also keep building in Nature’s way.

Victor So I think part of the, really the, the, the drive-home point is that there is a huge expanding human footprint that these hazards are hitting. We’re looking around going, holy shit, the world’s on fire. We’re having all these disasters. We have wildfires in the news. Tornadoes, hail, hurricanes. We just saw a massive heat wave in the west. That was well beyond anything we’ve ever recorded. We’re very certain that climate change had some component, some piece to that. 

But—what does this other piece of us just having so many more assets, so many more things to hit, these extreme weather disaster—by these extreme weather events, and how much is that contributing to the overall picture of economic loss not only in the U.S., but in the world? 

David Well, are there any positive trends in the way people are building and living in these increasingly vulnerable areas? 

Victor I haven’t seen anything. In fact, it seems after these disasters occur, we simply go back and build half-assed construction with very, very little oversight. You know, like, what? 

Building codes and structures, unfortunately, right, those are set at the local level. And so there’s no federal mandate, right, of “Oh, you live in Oklahoma City, you have to have a tornado or a house that can withstand an F3 tornado.” None of that exists in the United States, right? 

And yet that costs money. I get it. But it’s a long term investment, okay? Would you rather be paying for the disaster in 25 years, or put up the money up front, and invest in a more resilient infrastructure that’s going to be less prone to these types of events in the future? 

David I mean, we as a species have never been great at anticipating—like, we still smoke, we still don’t exercise. I mean, we know, right? We still don’t really take climate change seriously. I mean, we should have started 40 years ago. 

Victor Yes, I have—I would not argue with that. I think it’s—where, when do you get to the point? What is the level of disaster that has to occur in order for us to go—Yep, okay, we need to do something now, versus, you know, Oh, we just had another six standard deviation anomaly heat wave in the Pacific Northwest. And British Columbia is on fire, literally on fire right now. What do you do, you know? 

And, as usual in the world of climate chaos, people without a lot of money get hit first and worst.

Victor The people that are going to be most impacted by places—like, by most of the impacts of climate change—drought, flooding, sea level rise are going to be areas that are very, very socioeconomically disadvantaged. When, as a species, do we make that critical call of like, “Okay, we’re serious now. We weren’t before, but we’re serious now.” And is when that happens, is it too late? 

OK. So now you know that what’s traditionally known as Tornado Alley is shifting—or maybe I should say growing—into the more vulnerable, more populous states to the East. And that tornadoes form super fast; they’re not like hurricanes, where we see it coming a week before it hits. OK. So what are you supposed to do?

Well, about an hour before the tornado, your phone, or the radio or TV, might announce a tornado watch. That’s when the conditions are perfect for tornadoes to form, but nobody’s seen one yet.

A tornado warning means that somebody’s actually spotted one. 

Victor For most people, it’s as simple as get to the lowest floor in your home. If you don’t have a basement, that’s okay. Just get to the lowest floor and put as many walls between you in the tornado as possible. That’s it. So if that’s an interior closet, great, that’s a bathroom, great, if it’s underneath stairs, great, just get to the lowest floor. That will give you a very, very high likelihood of surviving even a strong tornado if you take that. 

The other thing that we tell people is that it’s not a bad idea to have a bicycle helmet in there. Most of the casualties we see are blunt force trauma to the head. So what a better move than just putting a bike helmet on, you know, and crouching down into your—

David Wow! 

Victor Yeah, yeah. In your severe weather safety kit, whether it’s water, batteries, flashlight—bike helmets are cheap, pick up a bike helmet and put a bike helmet on. That way, you have some sort of cushion between you and the flying debris. 

And Victor has special advice if you live in a mobile home. 

Victor Well, if you’re in a mobile home, don’t wait for the warning to be issued. You should be taking action at the watch stage, when the conditions are favorable, right? 

Many times, you’re lucky to get 10 or 15 minutes lead time when these events occur. 

You know, and I understand not everybody has the access or the means to just pick up and go somewhere. But there are community shelters in many places. You could perhaps go to a neighbor’s house or somebody that has, you know, a sturdier structure. But you don’t want to be in a mobile home during a tornado and you don’t want to be in a vehicle. Those are two areas you got to sort of figure it out. 

David So you—you have completed your storm chasing season for 2021, right? 

Victor Yes. We’re kind of all getting back. We’re getting unpacked, finally starting to sort through our pictures. And then by about Christmas, we, something sets in called SDS, or Supercell Deprivation Syndrome, where we start planning our trip, right, for next year. 

And so our pilgrimage again, you know, begins. 

You know what? I’m starting to get the impression that Victor Gensini really loves tornadoes.

Victor It’s like this giant orchestra, right, that’s playing. And every instrument has a role. And you’ve got to figure out what’s the moisture doing, what’s this doing? What’s the shear? I mean, there’s so many moving parts that, you know, just understanding the percussion is not enough. You got to understand the ensemble. And that’s what makes this problem so challenging. 

David Well, if it were up to me, I would suggest that you look at mid-levels for rotation and increase the PRF. 

Victor I love it.