0:00:12 > 0:00:15Our planet is home to some spectacular natural wonders.
0:00:19 > 0:00:24Yet exactly how and why they form is still a mystery.
0:00:27 > 0:00:33But now new camera technologies are revealing their inner workings
0:00:33 > 0:00:34in stunning detail.
0:00:38 > 0:00:42My name is Dr Helen Czerski and I'll be looking at how
0:00:42 > 0:00:47these extraordinary images are transforming our understanding
0:00:47 > 0:00:49of the natural world.
0:00:53 > 0:00:54In this programme,
0:00:54 > 0:00:59we'll be looking at the latest scientific insights into tornadoes,
0:00:59 > 0:01:02the fastest winds on the planet,
0:01:02 > 0:01:08unpicking the eyewitness footage that reveals the complex atmospheric
0:01:08 > 0:01:10conditions that create tornadoes...
0:01:11 > 0:01:14..the radar data, showing how they're formed,
0:01:14 > 0:01:16deep within the storm...
0:01:17 > 0:01:22..and the experiments investigating the immense destructive forces
0:01:22 > 0:01:24they generate.
0:01:24 > 0:01:27- MAN:- The whole house came apart!
0:01:27 > 0:01:30And as we observe these monster weather events and record them
0:01:30 > 0:01:33in ever more sophisticated detail,
0:01:33 > 0:01:37we're really starting to understand and appreciate not just their power,
0:01:37 > 0:01:39but also their subtlety.
0:02:04 > 0:02:06I don't know what to make of these stringy little features.
0:02:08 > 0:02:10Professor Josh Wurman and his team
0:02:10 > 0:02:13are from the Centre for Severe Weather Research
0:02:13 > 0:02:14in Boulder, Colorado.
0:02:17 > 0:02:22Each spring, they spend weeks at a time chasing tornadoes,
0:02:22 > 0:02:26trying to get their instruments as close as safely possible
0:02:26 > 0:02:30in a bid to try and understand how and why they form.
0:02:32 > 0:02:35The reason we're out here studying tornadoes and the reason why we're
0:02:35 > 0:02:39driving tens of thousands of kilometres is to make a major step
0:02:39 > 0:02:41in understanding how tornadoes form
0:02:41 > 0:02:43so that better predictions can be made in
0:02:43 > 0:02:47the future. If we can increase the lead time,
0:02:47 > 0:02:50people and families will have those several extra critical minutes
0:02:50 > 0:02:53to get to better shelters, get to their basements,
0:02:53 > 0:02:56or even get to community hardened shelters.
0:02:59 > 0:03:01I join them on one such hunt.
0:03:04 > 0:03:08We track storms across the States for ten days...
0:03:11 > 0:03:15..encountering some of the most astonishing weather
0:03:15 > 0:03:16I've ever experienced.
0:03:16 > 0:03:19But nothing prepared me for the moment
0:03:19 > 0:03:21when I finally came face-to-face...
0:03:23 > 0:03:24..with a tornado.
0:03:27 > 0:03:33A 2km-high spinning vortex of cloud,
0:03:33 > 0:03:35tearing across the countryside.
0:03:41 > 0:03:44- We're getting out? - 'It's 3km right now.'
0:03:48 > 0:03:50So this is it.
0:03:50 > 0:03:51And it's enormous!
0:03:54 > 0:03:57I had no idea it would look that big.
0:03:57 > 0:04:01It's just amazing. And here it's almost calm.
0:04:01 > 0:04:05But over there, those winds are going at hundreds of miles per hour,
0:04:05 > 0:04:08pushing stuff right up into the heart of the storm.
0:04:10 > 0:04:12I can't stop looking at it, it's incredible!
0:04:18 > 0:04:20It actually hits me a little bit here watching that again,
0:04:20 > 0:04:24because it was the biggest thing I had ever seen.
0:04:24 > 0:04:26It reset the scale of the sky.
0:04:26 > 0:04:30We think the clouds are a long way up but until you see a single thing
0:04:30 > 0:04:32that connects the ground to the clouds,
0:04:32 > 0:04:35you don't realise how big that is and that was all anyone could say,
0:04:35 > 0:04:37"How big is that?"
0:04:40 > 0:04:42'As surprising as the violence of these things
0:04:42 > 0:04:43'is how little time they last.
0:04:43 > 0:04:45'This one lasted just ten minutes,
0:04:45 > 0:04:47'we drove up, we filmed it, and then it was gone.'
0:04:47 > 0:04:52That was it. The trick of studying these things is being there at that
0:04:52 > 0:04:55moment, just when all the drama has come together.
0:04:56 > 0:04:59Capturing what happens in that moment
0:04:59 > 0:05:01is Josh's focus and will bring
0:05:01 > 0:05:05scientists one step closer to the ultimate goal -
0:05:05 > 0:05:09being able to predict exactly when a tornado will strike.
0:05:23 > 0:05:26The key is to work out how the complex flow of winds
0:05:26 > 0:05:30in the atmosphere comes together to form a tornado.
0:05:32 > 0:05:34Here at Birmingham University,
0:05:34 > 0:05:38Chris Baker and his colleagues build small-scale tornadoes,
0:05:38 > 0:05:41to study the effects of these unique winds.
0:05:43 > 0:05:45What we are looking at here
0:05:45 > 0:05:48is the flow visualised by some smoke,
0:05:48 > 0:05:51and we can see the swirl on the smoke
0:05:51 > 0:05:54and the smoke being dragged upwards.
0:05:59 > 0:06:02Tornadoes are swirling masses of air
0:06:02 > 0:06:06that move in towards the centre and then move upwards.
0:06:10 > 0:06:14In the lab, fans create that rotation and uplift.
0:06:17 > 0:06:21The mystery is how this movement is generated in nature.
0:06:25 > 0:06:29How these 2km-high vortices can form just through
0:06:29 > 0:06:33the interaction of atmospheric winds and pressure differences.
0:06:35 > 0:06:39And for that, you need to study them in the real world.
0:06:52 > 0:06:55Tornadoes can strike almost anywhere in the world.
0:07:01 > 0:07:04This tornado struck a highway in Taiwan.
0:07:06 > 0:07:07- WOMAN:- Oh, my God!
0:07:09 > 0:07:12Even the residents of Birmingham...
0:07:12 > 0:07:15- MAN:- No way. There's a tornado!
0:07:15 > 0:07:17..have the occasional brush with these fierce weather events.
0:07:17 > 0:07:19Look at it, man. It's everywhere!
0:07:24 > 0:07:26But there is one place above all
0:07:26 > 0:07:31that has become the natural laboratory for studying tornadoes.
0:07:31 > 0:07:35The ones that we hear about most often, because they're the largest
0:07:35 > 0:07:38and most destructive, is here in North America.
0:07:38 > 0:07:41It's not the whole country, it's one specific place,
0:07:41 > 0:07:43Tornado Alley, and that is a stripe that goes
0:07:43 > 0:07:46from northern Texas through Oklahoma, Kansas,
0:07:46 > 0:07:48Nebraska and into South Dakota
0:07:48 > 0:07:50and the tornadoes form here because of
0:07:50 > 0:07:54a very specific set of conditions that can happen in this region.
0:07:58 > 0:08:02This part of the world is witness to devastating weather events.
0:08:06 > 0:08:10Nathan Edwards was on a storm-chasing holiday in the US
0:08:10 > 0:08:14when he captured these incredible clouds.
0:08:14 > 0:08:16Look at that.
0:08:16 > 0:08:18- Wow.- Oh, look at that!
0:08:29 > 0:08:31This is a supercell.
0:08:33 > 0:08:37A special type of thunderstorm where tornadoes are born.
0:08:37 > 0:08:40Pretty darn strong winds coming up just over there.
0:08:40 > 0:08:43The incredible structures we can see here
0:08:43 > 0:08:47reveal the dangerous combination of air masses and wind patterns
0:08:47 > 0:08:51that make this place such a breeding ground for tornadoes.
0:08:56 > 0:08:59David Schultz, from the University of Manchester,
0:08:59 > 0:09:02is a meteorologist and an expert on the conditions
0:09:02 > 0:09:04that lead to such incredible storms.
0:09:06 > 0:09:09So, imagine that we're standing here on the Rockies,
0:09:09 > 0:09:10looking out over
0:09:10 > 0:09:12the Great Plains to the east.
0:09:12 > 0:09:16What we see down there is warm, moist air,
0:09:16 > 0:09:18flowing up from the Gulf of Mexico.
0:09:18 > 0:09:21Up here, where we are, in the Rockies,
0:09:21 > 0:09:25we have dry air that flows out over this moist air.
0:09:25 > 0:09:28The boundary between these two air masses
0:09:28 > 0:09:30produces what we call the lid.
0:09:30 > 0:09:35The lid is essential for making the storm so powerful because it traps
0:09:35 > 0:09:36that energy,
0:09:36 > 0:09:41that warm, moist air, underneath the lid until it's ready to explode and
0:09:41 > 0:09:45then we can have the development of this supercell thunderstorm.
0:09:49 > 0:09:53This amazing, almost circular, disc-shaped cloud
0:09:53 > 0:09:57is where the air is forcing its way through the lid.
0:10:02 > 0:10:05Once through, the rising air accelerates upwards
0:10:05 > 0:10:09and spreads into the turbulent clouds above,
0:10:09 > 0:10:12drawing air in and up into the storm,
0:10:12 > 0:10:15in tremendous flows called updraughts.
0:10:17 > 0:10:22The lid enables a supercell to build up huge amounts of energy.
0:10:26 > 0:10:31And the incredible upward surge of air fuelling the storm
0:10:31 > 0:10:33creates epic rain and hail.
0:10:35 > 0:10:37Wow!
0:10:37 > 0:10:40'It's something I experienced myself when chasing the storm.
0:10:43 > 0:10:46'And that was just a taste of what these storms are capable of.'
0:10:51 > 0:10:54HAIL CLATTERS
0:10:54 > 0:10:58The powerful updraughts of air can keep hail trapped within the cloud,
0:10:58 > 0:11:02building up layers of ice until they become so big and heavy that
0:11:02 > 0:11:05the storm can no longer hold them.
0:11:05 > 0:11:07- MAN:- Man, look at that massive thing.
0:11:07 > 0:11:09My God!
0:11:14 > 0:11:17It can create downpours of hail the size of baseballs.
0:11:21 > 0:11:22HAIL THUDS
0:11:23 > 0:11:25Not a time to be caught in the open.
0:11:38 > 0:11:42That intense rain and hail would also bring about the end
0:11:42 > 0:11:43of a normal storm.
0:11:45 > 0:11:48An ordinary storm only lasts about 20 or 30 minutes.
0:11:48 > 0:11:52That's because the air flowing into the storm rises up,
0:11:52 > 0:11:56forms the cloud but then, if there's any precipitation that forms,
0:11:56 > 0:12:00it falls back down into the updraught and that kills the storm.
0:12:02 > 0:12:05But not in the case of a supercell storm.
0:12:05 > 0:12:09Because a supercell rotates.
0:12:10 > 0:12:13Because the storm is spinning,
0:12:13 > 0:12:15all that intense rainfall and hail
0:12:15 > 0:12:18is no longer happening directly over the rising air.
0:12:20 > 0:12:25The supercell ensures its longevity because the rotation of the storm
0:12:25 > 0:12:27separates the updraught from the downdraught.
0:12:27 > 0:12:29You have the ascent, the updraught,
0:12:29 > 0:12:32circling around the storm, rising up,
0:12:32 > 0:12:35you have the descent, separated from that, coming in on the other side,
0:12:35 > 0:12:37circling around,
0:12:37 > 0:12:41and it's the separation between these two that ensures
0:12:41 > 0:12:43the longevity of the storm.
0:12:45 > 0:12:50Now we have a powerful, long-lived storm, primed to produce a tornado.
0:12:53 > 0:12:56All thanks to the mesmerising rotation
0:12:56 > 0:12:58captured in Nathan's footage.
0:13:00 > 0:13:02What creates this rotation is once again
0:13:02 > 0:13:05the specific conditions at work in the atmosphere.
0:13:07 > 0:13:10There's lots of things to see on this footage but there is one very
0:13:10 > 0:13:12important thing that you cannot see
0:13:12 > 0:13:14and that is the direction of the wind.
0:13:14 > 0:13:18Up at height, in this image,
0:13:18 > 0:13:20winds are going sideways like that,
0:13:20 > 0:13:23but down at the ground they are going back the other way and this is
0:13:23 > 0:13:25called wind shear,
0:13:25 > 0:13:27when the wind changes direction with height and you can
0:13:27 > 0:13:30see that if the winds are going to the right at the top and the left at
0:13:30 > 0:13:33the bottom, you start a rotation like this
0:13:33 > 0:13:35and the consequence of the wind shear
0:13:35 > 0:13:41is that you get a roll of air that is rotating around this way.
0:13:41 > 0:13:42If we look at the storm,
0:13:42 > 0:13:45that's not what we see in the storm we've got.
0:13:45 > 0:13:47Here it's rotating like that.
0:13:52 > 0:13:55So there has to be an extra step to generate rotation that goes around
0:13:55 > 0:13:56this way.
0:13:56 > 0:13:59If we think about that roll of air that the wind shear made,
0:13:59 > 0:14:03like this tube of pipe, so the wind is rotating around like this,
0:14:03 > 0:14:06the other thing we can't see in this storm is the updraughts, and that's
0:14:06 > 0:14:08air that's coming from the ground,
0:14:08 > 0:14:13pushing up into the storm, and if an updraught acts on our roll of air
0:14:13 > 0:14:15here, it can draw this upwards
0:14:15 > 0:14:18and so you are left with a single column with
0:14:18 > 0:14:22the air rotating around it like this and, just like we can see in the
0:14:22 > 0:14:25video, THIS is what starts the rotation of the supercell.
0:14:27 > 0:14:32This storm has all the ingredients needed to produce a tornado.
0:14:32 > 0:14:34But it never did.
0:14:42 > 0:14:44Why one storm produces a tornado
0:14:44 > 0:14:47when another very similar storm doesn't,
0:14:47 > 0:14:50is one of the main reasons that predicting tornadoes
0:14:50 > 0:14:52is so difficult.
0:14:55 > 0:14:58That's one of the big mysteries with the supercells.
0:14:58 > 0:15:0375% of these severe rotating supercells don't make tornadoes,
0:15:03 > 0:15:07only about a quarter do, so when we go out to observe them,
0:15:07 > 0:15:08what we're trying to learn
0:15:08 > 0:15:11are the real subtle differences between the ones that do
0:15:11 > 0:15:12and the ones that don't.
0:15:13 > 0:15:18The basic process of how a tornado forms in the lower part of a storm
0:15:18 > 0:15:21is known, but when it first develops,
0:15:21 > 0:15:23a tornado is very different to the ones
0:15:23 > 0:15:25we see tearing across the country.
0:15:31 > 0:15:34So, a tornado doesn't start life looking like that,
0:15:34 > 0:15:37it actually is part of a parent storm
0:15:37 > 0:15:41and it has to grow from the base of that cloud.
0:15:41 > 0:15:45To get a tornado started, you need wind shear.
0:15:45 > 0:15:48Now, this is different from the wind shear that we needed in order to
0:15:48 > 0:15:52produce the rotation associated with the supercell.
0:15:52 > 0:15:58That occurs from the surface to 6km or 7km above the Earth.
0:15:58 > 0:16:02For the tornado, we just need that over the lowest 1km.
0:16:02 > 0:16:04Wind shear at the lowest 1km
0:16:04 > 0:16:07gives you a sense of rotation like this.
0:16:07 > 0:16:11But we know a tornado has a sense of rotation like this.
0:16:13 > 0:16:15The fledgling tornado needs something
0:16:15 > 0:16:18to tilt it downwards and make it vertical.
0:16:18 > 0:16:23And a clue to what that might be was captured in a chance recording.
0:16:27 > 0:16:31Mike Lapera was recording what looked like a normal storm
0:16:31 > 0:16:32outside his shop.
0:16:35 > 0:16:36CHILD SCREAMS
0:16:36 > 0:16:37- MAN:- Go, go!
0:16:39 > 0:16:45The instantaneous burst of 160kph wind was not caused by
0:16:45 > 0:16:47a tornado, but by a micro burst.
0:16:49 > 0:16:54An extreme example of a downdraught, falling air within the storm.
0:16:57 > 0:16:59Brian Snyder was recording a storm...
0:17:01 > 0:17:03..when he captured this...
0:17:09 > 0:17:12A rarely seen micro burst in action.
0:17:12 > 0:17:15Plummeting air, crashing to the ground.
0:17:22 > 0:17:24And it's the action of downdraughts
0:17:24 > 0:17:27that's the final step in producing a tornado.
0:17:28 > 0:17:31How do we get from here to here?
0:17:31 > 0:17:33We need the downdraught,
0:17:33 > 0:17:38that tilts this vorticity into a vertical orientation.
0:17:39 > 0:17:42- MAN:- The tornado on the ground.
0:17:42 > 0:17:47But once a tornado is formed, what exactly are you looking at?
0:17:47 > 0:17:49It's not as simple a question as it sounds.
0:18:00 > 0:18:03This is forming right over our heads.
0:18:03 > 0:18:05One stormy afternoon,
0:18:05 > 0:18:08Jim Kenefick had an unwanted visitor.
0:18:08 > 0:18:10Oh, I want it gone.
0:18:10 > 0:18:13I don't want that thing touching down here.
0:18:13 > 0:18:16His footage captures the rare moment
0:18:16 > 0:18:19when a tornado first descends from the clouds.
0:18:19 > 0:18:21Just break up.
0:18:21 > 0:18:25And that gives a unique insight into why we can see tornadoes.
0:18:25 > 0:18:27Just break up.
0:18:27 > 0:18:29It's all thanks to what happens to air
0:18:29 > 0:18:33from the surrounding atmosphere as it's drawn into the tornado.
0:18:33 > 0:18:35I'm coming, I'm coming, I'm coming.
0:18:38 > 0:18:42Right at the core of a tornado, there is a region of low pressure,
0:18:42 > 0:18:46driving the whole system. And the reason you can see the tornado
0:18:46 > 0:18:48is all to do with what happens when warm, moist air
0:18:48 > 0:18:50that's moving along the ground
0:18:50 > 0:18:53reaches that area of low pressure.
0:18:53 > 0:18:54In this bottle here,
0:18:54 > 0:18:58I've got warm, moist air and I've pumped up the pressure inside
0:18:58 > 0:19:00and so when I release the top,
0:19:00 > 0:19:03we'll see what happens when you suddenly release the pressure.
0:19:03 > 0:19:04HISSING
0:19:04 > 0:19:06SHE LAUGHS
0:19:06 > 0:19:08And suddenly you get a cloud.
0:19:09 > 0:19:12And the reason for that is that as the pressure drops,
0:19:12 > 0:19:14the air cools and, suddenly,
0:19:14 > 0:19:17that means that all the water vapour that is inside there
0:19:17 > 0:19:18starts to condense.
0:19:20 > 0:19:23And when it condenses, it makes little particles and so you can see,
0:19:23 > 0:19:26very quickly, a cloud formed inside the bottle.
0:19:29 > 0:19:32As the warm, moist air is continuously pulled
0:19:32 > 0:19:35into the low pressure of the tornado,
0:19:35 > 0:19:38the water vapour within it cools and condenses...
0:19:40 > 0:19:44..forming a cloud that traces out the spinning column of air.
0:19:47 > 0:19:51What we're seeing is a tornado's own internal cloud.
0:20:03 > 0:20:07Where the tornado touches down, the wind speeds can be ferocious.
0:20:10 > 0:20:13Yet the rotation of their parent storm is relatively slow.
0:20:14 > 0:20:16So where do the intense wind speeds come from?
0:20:22 > 0:20:26Josh Wurman and his team gained an unexpected insight into the true
0:20:26 > 0:20:28strength of these winds.
0:20:28 > 0:20:29A tornado!
0:20:29 > 0:20:32- In front of us? - No, I can't see- BLEEP!
0:20:34 > 0:20:38Hunting a tornado at night is an even more dangerous business
0:20:38 > 0:20:39than usual.
0:20:39 > 0:20:43And one evening, whilst chasing through the dark streets of Russell,
0:20:43 > 0:20:44Kansas...
0:20:44 > 0:20:46Wow!
0:20:46 > 0:20:50..they found themselves directly in the path of the tornado.
0:20:50 > 0:20:52It got hit.
0:20:52 > 0:20:53The windows are broken.
0:20:53 > 0:20:58- RADIO:- 'We are OK, we are upright and we are...
0:20:58 > 0:20:59'Our radar has stopped.'
0:20:59 > 0:21:04This chance encounter became one of the very few times
0:21:04 > 0:21:05that the wind speed
0:21:05 > 0:21:10has ever been measured directly from the edge of the tornado.
0:21:10 > 0:21:13- I can still see the funnel. - It's still on the ground here.
0:21:13 > 0:21:15At just six metres above the ground,
0:21:15 > 0:21:20the wind was travelling at over 250kph.
0:21:20 > 0:21:22'OK, we are coming up towards you.'
0:21:24 > 0:21:26The clue to where these tremendous winds come from
0:21:26 > 0:21:29is found in the shape of the tornado itself.
0:21:36 > 0:21:39As it moves down out of the cloud,
0:21:39 > 0:21:42the column of spinning air is stretched and compressed...
0:21:43 > 0:21:46..forcing the tube to become narrower.
0:21:48 > 0:21:51Look at that! Look at that!
0:21:51 > 0:21:53That change in shape concentrates
0:21:53 > 0:21:56more of the energy of the tornado into its spin...
0:21:56 > 0:21:58Holy cow!
0:21:58 > 0:22:01..making it rotate much faster and driving the wind speeds
0:22:01 > 0:22:04up to hundreds of kilometres per hour.
0:22:04 > 0:22:06It's a tornado! Look at that!
0:22:08 > 0:22:11But the destructive ability of the tornado
0:22:11 > 0:22:15comes from more than the effect of such incredible wind speed.
0:22:16 > 0:22:21What's key is not just the physical impact of the winds
0:22:21 > 0:22:22but also the lift,
0:22:22 > 0:22:26as Scott McPartland and his fellow storm chasers witnessed.
0:22:30 > 0:22:34Oh, my God! Yeah, there's a house being destroyed over there.
0:22:34 > 0:22:36The house is coming apart!
0:22:36 > 0:22:39- Oh, these poor people! - Oh, my God!- Oh, my God!
0:22:39 > 0:22:41The whole house came apart!
0:22:44 > 0:22:46What's surprising is that the house is lifted
0:22:46 > 0:22:49BEFORE the main part of the tornado reaches it.
0:22:50 > 0:22:53Chris and his team are trying to work out
0:22:53 > 0:22:55exactly why tornado winds are so destructive.
0:22:55 > 0:22:57Within their chamber,
0:22:57 > 0:23:00they've placed a model building covered in sensors
0:23:00 > 0:23:03that can measure what happens when it encounters their tornado.
0:23:04 > 0:23:06At the moment, the generator is being used
0:23:06 > 0:23:09to measure the loads on the building,
0:23:09 > 0:23:12the pressures on the surface of the building,
0:23:12 > 0:23:14as the building's at different positions
0:23:14 > 0:23:16relative to the centre of the tornado.
0:23:17 > 0:23:22The key is the low pressures created by the fast-flowing winds.
0:23:24 > 0:23:28As the tornado moves across the building, it will go quickly,
0:23:28 > 0:23:30particularly over the eaves and the ridge -
0:23:30 > 0:23:34you get very low pressures at those areas.
0:23:34 > 0:23:39And the pressure inside the building can stay quite high and,
0:23:39 > 0:23:42if you've got a high pressure inside, a low pressure outside,
0:23:42 > 0:23:45that will either lift the roof or,
0:23:45 > 0:23:48if the roof is attached firmly and the foundations aren't,
0:23:48 > 0:23:51it will lift the whole building.
0:23:51 > 0:23:54The combination of the low pressure of the tornado
0:23:54 > 0:23:56and its forward motion
0:23:56 > 0:24:00means that the place with the strongest winds and greatest uplift
0:24:00 > 0:24:04is actually in front of the tornado as it approaches,
0:24:04 > 0:24:06just where this house is unlucky enough to be.
0:24:17 > 0:24:20In the face of such powerful forces,
0:24:20 > 0:24:22the amount of warning time is critical,
0:24:22 > 0:24:26giving people crucial minutes in which to take shelter.
0:24:26 > 0:24:28Funnel, right across the road!
0:24:28 > 0:24:30Right across the road!
0:24:30 > 0:24:35On May 22, 2011, a tornado hit Joplin.
0:24:35 > 0:24:37I have a large, destructive tornado!
0:24:37 > 0:24:40It measured over a kilometre across.
0:24:40 > 0:24:41Coming on the ground right here!
0:24:41 > 0:24:43Get the sirens going! Get the sirens going!
0:24:43 > 0:24:45- I'm telling you!- Back up!
0:24:45 > 0:24:46I am!
0:24:46 > 0:24:50And with wind speeds of over 300kph,
0:24:50 > 0:24:52the impact was brutal.
0:24:52 > 0:24:53Stop, stop!
0:24:53 > 0:24:56It was on the ground for less than 40 minutes
0:24:56 > 0:24:57but during that time,
0:24:57 > 0:25:01it tore a path of devastation through the heart of the city.
0:25:06 > 0:25:10Joplin Middle School was directly in the firing line.
0:25:18 > 0:25:21Thankfully, the school was deserted at the time.
0:25:31 > 0:25:36But across the city, the tornado took the lives of over 150 people.
0:25:41 > 0:25:45Many more would have died if not for the warning that was issued before
0:25:45 > 0:25:47the tornado hit.
0:25:53 > 0:25:56INDISTINCT RADIO CHATTER
0:25:56 > 0:25:59To improve that critical warning time,
0:25:59 > 0:26:01scientists like Josh are trying to capture
0:26:01 > 0:26:05the exact wind conditions that create the tornado...
0:26:05 > 0:26:06Sandra, when you get there,
0:26:06 > 0:26:09you may have to cut sort of through it, somehow.
0:26:09 > 0:26:13..by peering deep into the hidden heart of the storm.
0:26:16 > 0:26:18We are in the Doppler on wheels.
0:26:18 > 0:26:21A Doppler radar is able to send a beam of microwaves out
0:26:21 > 0:26:24through a tornado and scan back and forth
0:26:24 > 0:26:29and make three-dimensional maps of the winds and watch them evolve.
0:26:29 > 0:26:32And we're basically watching the process of tornado formation.
0:26:32 > 0:26:34And then, equally importantly,
0:26:34 > 0:26:37we can measure growth of humidities, the types of precipitation,
0:26:37 > 0:26:38which are really forcing those winds,
0:26:38 > 0:26:42they are causing the updraughts and downdraughts which may or may not
0:26:42 > 0:26:43evolve into a tornado.
0:26:48 > 0:26:51So the radar lets us measure the rain and hail,
0:26:51 > 0:26:53and that's what we're seeing here in red.
0:26:53 > 0:26:55This red is a hail area and surrounding this...
0:26:55 > 0:26:57Look at that go!
0:26:57 > 0:26:59At the tip of the hook, where we have this ball,
0:26:59 > 0:27:01is where the tornado is beginning to develop.
0:27:01 > 0:27:05And, eventually, we see it spinning there and we even see a clear eye.
0:27:05 > 0:27:07That green spot is the eye of the tornado.
0:27:11 > 0:27:15Capturing these moments, revealing the intricate details,
0:27:15 > 0:27:19has already improved warning times from only five minutes
0:27:19 > 0:27:22in the 1980s to nearer 15 now -
0:27:22 > 0:27:25minutes that save lives.
0:27:27 > 0:27:30But the drive to improve that continues.
0:27:32 > 0:27:36If we can increase the lead time from its current 13 minutes
0:27:36 > 0:27:39to about 20-minute warnings or even 25 or 30-minute warnings,
0:27:39 > 0:27:42people, families, who live in Tornado Alley
0:27:42 > 0:27:44can live here feeling safer,
0:27:44 > 0:27:48they can live here being safer and can weather the storm.
0:27:56 > 0:27:58The explosion in footage of tornadoes
0:27:58 > 0:28:01reveals a beauty and power that is
0:28:01 > 0:28:04both awe-inspiring and terrifying.
0:28:06 > 0:28:09The insights into the unusual combination of weather that creates
0:28:09 > 0:28:13tornadoes is improving warning times.
0:28:13 > 0:28:17But the exact conditions that lead to these violent storms
0:28:17 > 0:28:19are still elusive.
0:28:22 > 0:28:25Tornadoes are a reminder of the amount of energy there is in
0:28:25 > 0:28:28our atmosphere and the amount of destruction that it can cause
0:28:28 > 0:28:32if only a tiny fraction of it is focused in just one place.
0:28:32 > 0:28:36We are unlikely ever to be able to control these phenomena but,
0:28:36 > 0:28:39as we learn more and understand better, hopefully,
0:28:39 > 0:28:42we will be able to predict them.