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odintsov.info: NOVA: Hunt for the Supertwister: Movies & TV. Not Rated; Studio : PBS; DVD Release Date: June 29, ; Run Time: 60 minutes; Average. OkCupid is the only dating app that knows you're more substance than just a selfie—and it's free! Download it today to make meaningful connections with real . But today, experts are exploring the supertwister's complex inner workings in bold Apollo ZeroConspiracy - 60 min - ☆ Think about this: to date, only three.
I feel like we're in a twister movie. Josh has witnessed some of the most powerful supertwisters of recent years, including the May 3,storm that hit Moore, Oklahoma, where he recorded the fastest winds ever measured: When the massive supertwister first set down, it was in a field about 40 miles from Moore.
TV forecaster Gary England had a full hour to warn his audience. Do not try to ride this storm out in your home, unless you are trapped. Get in the center part of your house, a closet or bathroom. Cover it with pillows and blankets. Lots of pillows, lots of blankets, get in the bathtub, put the kids in the bathtub, get in on top of the kids.
From Channel 9's command center, Gary and his viewers could see exactly what was coming.
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Right now it may turn a little bit north of Norman. If it maintains itself, you folks in North May 3 rdthere was continuous coverage. They had helicopters up in the air filming the tornado, so people could watch the TV, see exactly where the tornado was.
They had radar, with fantastic capability, showing the path that this thing was going to take. So people knew what was coming. We've got it falling on the ground right now, right hand side, tornado on the ground right there. The green cloud, the green cloud, there it is.
After May 3, we had nearly 70 tornadoes in our viewing area, here in Oklahoma, and you know a lot of people killed, what, 8, structures destroyed? People pay attention now. The May 3 rd supertwister was the most powerful on record. And yet, after it finally fizzled out What's that right in front of us? Josh Wurman and his team discovered yet another supertwister roaring over open country. During the May 3 rd outbreak there were at least 50 other tornadoes.
One of those was over four times as large as the one that went through the metropolitan area of Oklahoma City. Had that tornado gone through Oklahoma City, it would have caused a damage swath four times as wide, probably a mile wide or more, destroying many times more structures than were actually destroyed.
The May 3 rd'99 event is a major, major event to the people in Oklahoma and especially the people in Oklahoma City. But how many people outside that area realized what happened there? Realized the carnage that took place? It's not just powerful winds that make supertwisters so deadly. Once they form, they often keep on churning, staying on the ground an hour or more.
These so-called long-track supertwisters aren't confined to Tornado Alley. Inone paid a sudden and unwelcome visit to a small town on the east coast. It's coming this way, guys. I remember seeing this huge funnel cloud, and it was holding things in the air that were just whirling so fast.
And as they came to the top, you could recognize things like a tree, a couch, a desk.
Hunt for the Supertwister
You're expected, asked to take cover immediately. And we're looking at each other, thinking, "Is that a tornado? It was a supertwister, sweeping straight through the center of La Plata, Maryland. Then I remember this tangled mass of metal was coming right at me, I mean directly at my car. And briefly I thought, well, I'll probably get decapitated. And my car lifted two feet up in the air and actually moved under the CVS sign.
Still I say it sounded like a jet turbine engine; I can't even duplicate the sound. And the house started rumbling, shaking. The giant vortex sped through town. This tornado was moving at close to 60 miles an hour. That's a mile a minute. From here over to the buildings that are standing there, the tornado was probably through here in 15 seconds or less.
One minute everything is there, and then, 15 seconds or less, everything is destroyed. You go from almost no wind up to mile an hour wind and back down. As the tornado was ripping through downtown La Plata, just outside of town, Susan Erikson and her husband Erik were visiting the construction site of their new dream house. They had no idea a tornado was coming. The only thing we had heard on the news that day was thunderstorms.
And we had thought, "No big deal. I remember silence at that time, no birds, no anything. I just heard silence. And we were getting ready to leave, and then everything went blank. Susan came to in a pile of rubble, hearing the groans of her husband Erik.
Both my arms were broken, they weren't functioning correctly. So what I did was try to maneuver my legs, so that I could stand up and drag my arms up with me. I remember walking out of the house.
Luckily, some neighbors found Susan before she passed out again. The next thing she knew, she was in the hospital. It was between the two surgeries, before I went in for my orthopedic surgery on my arms, that they told me he had died. And they said he was in a morgue in Baltimore. Erik Erikson was one of five people killed by the supertwister that hit La Plata. Far from Tornado Alley, the monster storm carved a path of destruction 62 miles long, narrowly averting an unthinkable disaster.
If you were to have taken the La Plata, Maryland tornado and just moved it north about 30 or 40 miles, you would have gone from beltway to beltway, right across the Potomac and through the Nation's Capital. Rare as they are, supertwisters can strike anywhere, anytime. But no one knows why. In fact, scientists are stumped about what causes any tornado, large or small.
Unless they can solve the puzzle and figure out how a supercell thunderstorm creates a tornado, then predicting supertwisters will be impossible. But how do you decipher the inner workings of a tornado? Meteorology, in contrast to chemistry or biology, is not a good laboratory science. We can't produce an accurate representation, a controlled representation of a thunderstorm, and change the variables one by one to make tornadoes. No one can create a real tornado, either on the plains or in a lab.
But there is one place where scientists can play puppeteer with the weather: The closest approximations we have are computer simulations. And we try to build a digital, computational model of the tornado and see if we can change variables and have storms that produce tornadoes and ones that don't.
One of the leaders in tornado computer modeling is Lou Wicker. It doesn't have good rotation. We're not going to deploy. A little farther, team, a little farther. Peak the hill, peak the hill. Back then, researchers thought the best way to learn about a tornado was to leave special sensors in its path. That was the idea behind Toto, a weather station the size of an oil drum.
Lou took charge of getting Toto as close as possible to a tornado without wiping out the research team. In the '70s and the early '80s, we were just trying to understand what made storms work, sort of visually.
Now we're moving into an area where we're trying to understand the dynamics of storms. Inside storms, dynamics means how the individual blobs of air are all interacting with each other to produce the flow that becomes either the strong winds, or even the tornado, or even the things that produce hail. Based on years of weather research, Lou produces an amazingly detailed computer simulation, designed with scientists at the University of Illinois.
It reveals a familiar pattern: The clouds begin to spin and roil high in the sky. They descend closer to the ground, still swirling rapidly. Suddenly, the rotation narrows and intensifies, and touches down to earth. The question on everyone's mind is, "What triggers that final step? What makes the tornado form? Somehow, supercell thunderstorms are able to bring intense rotation and intensify that rotation near the surface. And we don't understand that process very well.
We know that before a tornado forms, there are areas of rotation in the thunderstorm. What we don't understand is how that rotation is brought down to the ground and intensified in a very short period of time in order to make a tornado.
In the search for a trigger, one of the primary suspects has been a burst of air descending from the storm, called a downdraft. The idea is that the downdraft wraps around the storm, tightening and intensifying the rotation. We think the downdraft is really important for producing the tornado, because it would help sort of squeeze the air from near the ground up into the updraft.
The air wraps around and sort of In the minutes before a twister forms, storm chasers often see a downdraft blasting a hole in the clouds toward the rear of the storm. Well, it's a very impressive storm. So far there's no tornado, but the structure looks quite good. We're seeing a very strong R. On the radar, it's still looking pretty good. But just as often, a tornado fails to materialize. There must be more to the story. It's very likely that in order to solve the tornado problem, we're going to need a lot more data than we have right now, because a lot of things are going on at small scales that we don't actually sample.
And so until we have that, it will remain a research problem. And so, every spring, storm chasers like Howie Bluestein hit the roads of Tornado Alley, all on the hunt for the tornado trigger. What we want to do is capture the formation of tornadoes in many, many storms.
We want to see precisely how the wind field is changing. We want to see what's happening to the temperature field and the humidity field for a lot of storms. Mobile Doppler radar is the key to mapping the swirling wind patterns that spawn tornadoes. Today's storm chasing teams often include at least two Doppler trucks so they can record the storm from multiple perspectives. Twenty five years ago we went out by ourselves.
Now when we go out, there's an armada of cars out there. There are a number of different mobile Doppler radars. And of course, the more vehicles you have out there, the more vehicles that need gas, the more people that have to run to the bathroom at bad times, and so on.
All the high-tech sensors and computers they haul around allow Josh and Howie to monitor tornadoes in fantastic detail. The only problem is this equipment doesn't like to travel. Radars, at some fundamental level, aren't really designed to be put on trucks and bounced around in severe storms. So we have a lot of problems with the complicated electronics, where things just shake and break apart. And we have shorts and things like that happening all the time.
We've broken our windshields now for the last two days. Our last one only lasted seven hours. When you're storm chasing, you have to be prepared for anything, whether it's treacherous road conditions, dust storms, or hail the size of baseballs.
That is a horse in front of us. Oh, look at that. Hey, hey, hey, hey, you guys running the truck The messy and unpredictable reality of storm chasing shifts into high gear on May 15, Josh and Howie lead separate teams on the hunt for tornadoes. May 15 th was incredibly complicated. We, and everyone else in the world, recognized that over the Texas panhandle the conditions were ripe for tornadic storms.
The conditions looked very, very good. For a storm chaser, "very, very good" means lots of wind shear. Today, a zone of low pressure is drawing warm moist air from the south into the Texas panhandle. Just above it, the jet stream is blowing even faster. The two air masses, crossing at different speeds and altitudes, produce wind shear. When there's wind shear, air near the ground begins to spin. If there's a thunderstorm in the area, it could take on this spin and perhaps go on to spawn a tornado.
As the chase begins, the team leaders must choose what part of the Texas panhandle looks most promising. A lot is riding on the decision. Well, we have a lot of anxiety, because it's a very high-stakes game. It's very expensive and time-consuming to go out after these storms, and they're fairly rare.
So, we really need to make these calls efficiently if we're going to capture these rare events, and we only have a few chances every year to do that. Josh decides to head north toward Dalhart, Texas. Now I can do my Lou Reed: His team needs to find an Internet connection to get an update on the weather. They find one in a restaurant in Shamrock, Texas.
Testing a 38 at Guadeloupe Pass. Will you look at that! Look at the back winds, and they're strong. It's going to be west of Amarillo. It's going to be Howie thinks the southern panhandle holds more promise. He also fears that up north, where Josh is headed, the road system is too sparse. I'm not sure I want to get caught up in those storms in the northern Texas panhandle.
They're going to go off into an area where the road network isn't too great. So Howie chooses to hang back near Amarillo, Texas, and wait for the storms to come to him. Having chosen the northern route, Josh lucks out. When the show begins, he's in perfect position. There's the tornado, looks nice. Oh yeah, oh yeah! Looking at the radar, you'll be able to see that rotation pretty clearly.
We intercepted six tornadoes on that day. And one thing that was fascinating about that storm was there were at least two occasions where there were two vigorous tornadoes on the ground at the same time. This is the first time that twin tornadoes have ever been captured with ground-based mobile radar. I cannot miss you, ma'am. Having two tornadoes in close proximity like that maintaining their vigor is very unusual.
We've never seen that before in all our years of radar intercepts. Josh and his team take home the prize. They've captured high quality evidence on multiple tornadoes, including rare twin twisters. In the meantime, about miles to the south, the weather is depressingly fine, and Howie has captured nothing.
It doesn't like me, or she doesn't like me. It's the storm chaser's nightmare, to know that you made a good forecast in general, but there's a tornadic storm going on that you could have gotten that's just miles away. You've driven all this great distance, made what you thought was a really good forecast, and you've missed a tornado by an hour or two hours. After hours of waiting around the southern panhandle, watching the clouds on radar, things are looking bleak, when, finally, Howie gets an encouraging phone call.
We are sitting in Hedley, right now, watching it on our radar—fantastic. That's what we've been watching. Okay, thanks a lot. Okay, I'm going to come out and look at it. We have some good news. Wow, that looks good. If the sun could go behind there, I could get a picture. What Howie sees is the vertical edge of a thunderstorm pushing up through the atmosphere and beginning to rotate, a supercell.
All of a sudden, one of the storms suddenly went up and became a supercell. It's as if someone had turned the switch on. Looks like a good supercell. We're going to have to move here. We're having trouble with the computer. Even as the sun is setting, Howie's team tracks a series of storms back to the outskirts of Shamrock.
Finally, a familiar pattern appears on the radar screen, a hook shape often associated with a strong, swirling downdraft and a tornado. It may be strengthening, and it may be another tornado, possibly. And we're collecting data right now. The Doppler radar reveals that just a few miles away a tornado is churning. I hate to not be able to see it. If we didn't have the radar, we wouldn't be here.
I've got to get back in. There's very, very strong inflow into the storm right now. It's extremely dangerous to be so close to a tornado, especially after dark. We have a local sheriff If the storm had been moving at 35 miles per hour, coming right toward you, and you were near the storm, but you didn't know precisely where the storm was with respect to where you were, you could have been in great danger. Howie's eyes couldn't pierce the darkness to see the tornado, but his Doppler radar dish could.
The radar kept Howie and his team safe, but did it capture any important clues to the tornado mystery? To find out, Howie and Josh will both spend months, even years, back at their labs, dissecting the evidence they collected on this, the most productive day of the season.
The storm chasers will pack up their equipment in early June. But miles away, in the northern reaches of Tornado Alley, the show is far from over. And the stage is set for a rare appearance by the elusive supertwister. The time is late June,and the place is South Dakota.
There's no Doppler, no data and no theories. Instead, there are tornado tourists. I think it's one of those things that I'm actually here hoping to see our first tornado. You know, we're not going right underneath these things.
We're just hoping to see something, you know, from a distance.
odintsov.info: NOVA: Hunt for the Supertwister: Movies & TV
It is the battle to understand what triggers the most terrifying and destructive tornadoes, the Supertwisters. A two hundred and fifty or a three hundred mile an hour wind can only be compared to those that might be experienced on the fringes of a nuclear explosion.
It may be strengthening, and there may be another tornado possibly. Got to get back in, there's a very, very strong in flow in to the storm right now. At stake is something that could not be more important, people's lives. Hundreds are killed and injured each year by these Supertwisters.
For any one living where these tornadoes strike, any extra warning time could quite literally save lives. Tonight, Horizon tells of the struggle to find a way of giving those few precious extra minutes warning, that might not save properties or possessions, but could offer people just enough time to reach shelter and safety.
Ina small town on the east coast of America received an unwelcome visitor. It's coming this way guys. I remember seeing this huge funnel cloud. And it was holding things in the air that were just whirling so fast. And as they came to the top you could recognise things, like a tree, a couch, a desk. And we're looking at each other thinking is that a tornado. It was a giant tornado. And it swept straight through the heart of La Plata, Maryland.
And I remember this tangled mess of metal was coming right at me, I mean directly at my car. And briefly I thought oh I'll probably get decapitated. And my car lifted two feet up in the air, and actually moved to under the CVS sign. Still I, I say it sounded like a jet, turbine engine, I can't even duplicate the sound. The house started rumbling, shaking. The monster tore through the town. This tornado was moving close to sixty miles an hour, that's a mile a minute from, from here over to the buildings that are standing there.
The tornado was probably through here in fifteen seconds, or less. It's amazing, you go from almost no wind up to two hundred mile an hour wind and back down. Yet as the tornado was ripping through La Plata, just outside of town, Susan Erikson and her husband Eric were oblivious to the unfolding disaster. They were visiting the construction site of their new dream house. The only thing we had heard on the news that day was thunderstorms, and we had thought no big deal. We had just come up from the basement, I remember silence, at that time no birds, no anything, I just heard silence.
We were getting ready to leave and then everything went blank. Susan came too in a pile of rubble, and heard the groans of her husband Eric. Both my arms were broke, they weren't functioning correctly.
So what I did was try to manoeuvre my legs so that I could stand up and drag my arms up with me. I remember walking out of the house. Some neighbours found Susan before she passed out again. When she was recovering in hospital, they gave her news of her husband. It was between the two surgeries before I went in for my orthopaedic surgery on my arms that they told me he had died. The rescue team they said I shouldn't have lived, I really should have died with Eric because I was directly behind him.
There is no rhyme or reason why I was left behind, I just truly don't know if I was blown back where he was caught under the rubble or what exactly happened. Eric Erikson was one of five people killed that day, by one of nature's most violent forces. Because what had struck the town of La Plata was no normal tornado. It was a Supertwister. Some violent storms, like hurricanes, are so huge they cover thousands of square miles.
They can even be seen from space. There can be literally days of warning before they strike. But tornadoes are altogether different. Compared to hurricanes they cover a much smaller area, and they form at incredible speed, it is this that makes them so deadly.
Tornadoes are measured on a five point F scale. The weaker ones are classed as F zeros, or F ones. Yet even these can reach speeds of over a hundred miles an hour. And it's not just the force of the wind that makes tornadoes so feared, but what the wind can carry with it. Hailstones the size of golf balls can wreck a car, and kill a person.
At a university in Lubbock, Texas, scientists have recreated the power of a tornado using compressed air, looking at the impact of missiles travelling at a hundred miles per hour on bricks, plate glass and sheet metal. They hurl the kind of debris that would be picked up by a tornado and assess the damage they would cause.
Few would survive a missile travelling through the air at a hundred miles an hour, and that can be just a normal tornado, but in some cases winds are much, much greater. Rated F four and F five on a five point scale, these are the deadliest of tornadoes. They do happen and they happen nearly every year, and the force of an F five comes down your street, if you're not in a safe room or basement or cellar you, you're probably going to be history.
These rare beasts are known as Supertwisters. They can unleash enormous energy and can generate ground level winds about two hundred miles per hour. The winds of strong tornadoes are among the strongest forces that we ever see in nature. The over pressures that are experienced by buildings during a two hundred and fifty or three hundred mile an hour wind can only be compared to those that might be experienced on the fringes of a nuclear explosion.
In MayWurman measured the fastest Supertwister ever recorded. It first set down in a corn field, about forty miles south west of Oklahoma City, a city of more than half a million people.
Unusually for a tornado, TV forecaster Gary England had a full hour to warn his audience. Do not try to ride this storm out in your home unless you are trapped. Get in the centre part of your house, a tub in your bathroom, cover it with pillows and blankets, lots of pillows, lots of blankets, get in the bathtub, put the kids in the bathtub, get in on top of the kids. From Channel 9's command centre, England and his viewers could see exactly what was coming.
Right now it may turn a little bit north of Norman, see if it maintains itself. They served us with continuous coverage, they had helicopters up in the air filming the tornado so people could watch the TV, see exactly where the tornado was. They had radar with fantastic capability showing the path that this thing was going to take.
So people knew what was coming. We have tornado on the ground, right there, right inside. Tornado on the ground May 3rd, you know we had nearly seventy tornadoes in our viewing area here in Oklahoma.
And you know a lot of people killed, what eight thousand structures destroyed, people pay attention now. Out on the road Josh Wurman got close enough to measure the wind speed. It was an astonishing three hundred and one miles per hour. It made the Oklahoma Supertwister the most powerful ever recorded.
A three hundred mile an hour wind is not three times as strong as a hundred miles an hour. It is nine times as strong. They can cause such complete destruction, and then it's apparently almost instantaneous, one moment you're out there on an afternoon, and twenty minutes later your house can be gone.
A wind travelling at three hundred miles per hour would be capable of flattening practically anything in its path. This power makes the Supertwister especially dangerous. The only way to guarantee survival is not to be there when they strike, just a few minutes extra warning time could mean the difference between reaching safety or death. And finding those few extra minutes could be all the more vital because there's something making the situation even more critical.
Cities in Tornado Alley are becoming bigger targets. I think we have reached a critical point here, where as we are now expanding our cities bigger and bigger, so the targets for tornado hits are bigger and bigger. And the fear that I have is that now that the city is going to continue to get bigger, the houses still stay the same in terms of construction, now we're going to start having an upswing in the number of fatalities.
So let's just picture this, let's say it's two in the afternoon, largest tornado comes in to a city. Moving towards a school that has five hundred children in it.
What's going to happen when that warning goes out? There's going to be hundreds of parents trying to rush to that school to get those kids out. And it will take the school out, it will take the parents out. And mark my words it will happen. It's fears like this that put huge pressure on scientists to come up with a solution, an effective way of predicting Supertwisters. If an answer could be found then hundreds of lives would be saved. All Supertwisters are produced by thunderstorms.
But so far it has proved impossible to predict which storms will go critical and which ones won't. There are several limitations to our knowledge at this point. And the reason for that is that while we have made some progress in understanding physical processes on the scale of thunderstorms, we don't understand nearly enough from a scientific perspective.
We all wish that we could pin point the exact location where severe weather will strike, and tell people what time it's going to strike. But the science hasn't reached that point yet. The storm centre monitors the atmosphere across the whole of North America, and then uses computer programs to try to predict where the most dangerous storms will develop. And if the general conditions look strong for tornadoes, the storm centre will issue a so-called tornado watch.
But a tornado watch can cover tens of thousands of square miles, areas so wide that these warnings are often viewed as meaningless.
Only after radar sees a tornado is actually forming, does a precise tornado warning go out. This is a major tornado, wind speed we don't know. But by then it can often be too late. When we issue the warning, the warning is supposed to mean that that tornado has been detected, it is there. We want to be able to take it to that next step where we can say we've got this really bad storm, conditions are right for a tornado to develop. Where we're at right now, when you've detected it it's occurring.
The sad fact is that official tornado warnings often come too late. On average only twelve minutes before a Supertwister strikes. Not enough time to evacuate a school or hospital. Finding out what turns a thunderstorm in to a Supertwister had become a vital scientific challenge. This has become the mission for a very select band of scientists, known as the storm chasers. Howie Bluestein has been chasing tornadoes for over twenty-five years in the twister prone reason of America's central plains, known as Tornado Alley.
When he started out Howie's operation was certainly lo-tech. There were no laptop computers, no global positioning system, nor mobile phones. But over time the storm chasers' arsenal has expanded. Twenty-five years ago we went out by ourselves. Now when we go out there is an armada of cars out there. There are a number of different mobile Doppler radars. And of course the more vehicles you have out there the more vehicles that need gas, and more people that have to run to the bathroom at bad times.
Today the storm chasers main weapon is a Doppler radar dish mounted on the back of a truck. Doppler radar uses sound waves to sense the movement of air and moisture in remarkable detail, even picking up patterns of dust clouds and insects. This equipment is the most accurate way of mapping the complex swirling wind patterns that make up a tornado. Today storm chasing teams often include at least two of these Doppler trucks so they can record the storm from different angles.
Howie was the first to put a Doppler radar dish on the back of a truck, and catch data off tornadoes in action. The storm chasers hope that all this data collecting equipment will one day help crack the problem of predicting Supertwisters. What we want to do is capture the formation of tornadoes in many, many storms.
We want to see precisely how the wind field is changing, we want to see what's happening to the temperature field and the humidity field for a lot of storms. A big problem is this equipment doesn't like to travel, and when you're storm chasing you have to be prepared for anything. There's a horse in front of us. Oh look at that. They face treacherous road conditions, dust storms, and hail the size of golf balls.
Radars at some kind of level aren't really designed to be put on trucks and bounced around in severe storms, and so we have a lot of problems with the complicated electronics, where things just shake and break apart, and we have shorts, things like that happening all the time. Not much I can do about that. So we've broken our windshields now for the last two days, our last one only lasted seven hours, that's very frustrating.
The simple fact is that tornadoes are so unpredictable tracking them is still hit or miss. Storm chasers like Howie Bluestein consider themselves lucky if they intercept one or two good tornadoes each year. With such a haphazard way of collecting information it has always seemed likely that the Supertwister will hang on to its secrets.
Those few vital extra minutes of warning time would remain elusive and lives would continue to be lost. But one man thought he might have a solution. Kelvin Droegemeier's aim was to use a new computer model to provide early warnings, not of Supertwisters themselves, but of the conditions that spawn them. My dream is to be able to detect tornadoes down at very fine scales, to anticipate tornadoes, a half an hour before they occur. We're talking about a storm forming to produce a tornado over a country or a city, it's a whole different ball game.
Droegemeier's starting point was the knowledge that Supertwisters are all formed under the bellies of thunderstorms, in particular a hugely violent type known as a super cell. A super cell is a vast rotating column of air. These huge bodies can be twenty miles across and sixty thousand feet high.
More than double the height of Mount Everest. Every Spring, warm moist air surges up from the Gulf of Mexico, pushing in to cool dry air from the north. Strong winds coming in from different directions at different speeds causes the air to start rotating. And as the energy becomes more intense, a super cell is born. But only in some of these super cells will an angry tail emerge to reach down and touch the ground.
The main problem is understanding this final step, what is the precise mechanism by which a super cell gives birth to a Supertwister? Somehow super cell, thunderstorms, are able to bring intense rotation and intensify that rotation near the surface. And we don't understand that process very well. We know that before a tornado forms there are areas or rotation in the thunderstorm.
What we don't understand is how that rotation is brought down to the ground and intensify in a very short period of time in order to make a tornado.
In the search for a trigger one of the prime suspects has been a burst of air descending from the storm called a downdraft. A blast of air that descends and picks up speed as it falls towards the ground.
We think the downdraft is really important for producing the tornado because it helps sort of squeeze the air from near the ground up in to the updraft. The downdraft kind of comes around and squeezes the air in the front and the back together, it kind of squirts the air up off the ground.PBS NOVA S31E15 Hunt for the Supertwister
In the minutes before a twister forms, storm chasers have often seen a downdraft blasting a hole in the clouds, toward the rear of the storm. That's a very impressive storm, but the structure looks quite good, we're seeing a very strong RFD coming down. But at this part there's still no tornado.