WEBVTT 00:00:06.969 --> 00:00:09.197 They call me the tornado chaser. 00:00:09.197 --> 00:00:11.716 When the wind is up and conditions are right, 00:00:11.716 --> 00:00:15.159 I get in my car and follow violent storms. 00:00:15.159 --> 00:00:20.259 "Crazy," you say? Perhaps, but really I chase these sky beasts to learn about them. 00:00:20.259 --> 00:00:22.837 I want to share with you what I know. 00:00:22.837 --> 00:00:27.730 Tornadoes are rapidly rotating columns of air that form inside storms 00:00:27.730 --> 00:00:30.874 that connect with the ground via a funnel of cloud. 00:00:30.874 --> 00:00:33.382 When that happens, they tear across the Earth, 00:00:33.382 --> 00:00:36.521 posing a huge threat to life and property. 00:00:36.521 --> 00:00:40.258 Because of this, there's a great deal of research into these phenomena, 00:00:40.258 --> 00:00:44.986 but the truth is, there's still a lot we don't know about how tornadoes form. 00:00:44.986 --> 00:00:47.371 The conditions that may give rise to one tornado 00:00:47.371 --> 00:00:50.188 won't necessarily cause another. 00:00:50.188 --> 00:00:54.466 But we have learned a lot since people first started recording tornadoes, 00:00:54.466 --> 00:00:58.593 like how to recognize the signs when one is brewing in the sky. 00:00:58.593 --> 00:01:00.579 Are you coming along for the ride? 00:01:00.579 --> 00:01:05.035 Tornadoes begin with a thunderstorm but not just any thunderstorm. 00:01:05.035 --> 00:01:09.854 These are especially powerful, towering thunderstorms called supercells. 00:01:09.854 --> 00:01:13.698 Reaching up to over 50,000 feet, they bring high force winds, 00:01:13.698 --> 00:01:19.444 giant hailstones, sometimes flooding and great flashes of lightning, too. 00:01:19.444 --> 00:01:22.329 These are the kinds of storms that breed tornadoes, 00:01:22.329 --> 00:01:26.328 but only if there are also very specific conditions in place, 00:01:26.328 --> 00:01:31.217 clues that we can measure and look out for when we're trying to forecast a storm. 00:01:31.217 --> 00:01:35.495 Rising air is the first ingredient needed for a tornado to develop. 00:01:35.495 --> 00:01:38.261 Any storm is formed when condensation occurs, 00:01:38.261 --> 00:01:40.361 the byproducts of the clouds. 00:01:40.361 --> 00:01:42.392 Condensation releases heat, 00:01:42.392 --> 00:01:46.676 and heat becomes the energy that drives huge upward drafts of air. 00:01:46.676 --> 00:01:50.021 The more condensation and the bigger the storm clouds grow, 00:01:50.021 --> 00:01:52.808 the more powerful those updrafts become. 00:01:52.808 --> 00:01:57.369 In supercells, this rising airmass is particularly strong. 00:01:57.369 --> 00:02:01.957 As the air climbs, it can change direction and start to move more quickly. 00:02:01.957 --> 00:02:05.037 Finally, at the storm's base, if there is a lot of moisture, 00:02:05.037 --> 00:02:07.781 a huge cloud base develops, giving the tornado 00:02:07.781 --> 00:02:11.451 something to feed off later, if it gets that far. 00:02:11.451 --> 00:02:15.574 When all these things are in place, a vortex can develop enclosed by the storm, 00:02:15.574 --> 00:02:20.520 and forming a wide, tall tube of spinning air that then gets pulled upwards. 00:02:20.520 --> 00:02:22.844 We call this a mesocyclone. 00:02:22.844 --> 00:02:25.277 Outside, cool, dry, sinking air 00:02:25.277 --> 00:02:28.106 starts to wrap around the back of this mesocyclone, 00:02:28.106 --> 00:02:31.229 forming what's known as a rear flank downdraft. 00:02:31.229 --> 00:02:34.547 This unusual scenario creates a stark temperature difference 00:02:34.547 --> 00:02:38.539 between the air inside the mesocyclone, and the air outside, 00:02:38.539 --> 00:02:42.680 building up a level of instability that allows a tornado to thrive. 00:02:42.680 --> 00:02:45.558 Then, the mesocyclone's lower part becomes tighter, 00:02:45.558 --> 00:02:48.240 increasing the speed of the wind. 00:02:48.240 --> 00:02:51.539 If, and that's a big if, this funnel of air moves down 00:02:51.539 --> 00:02:55.412 into that large, moist cloud base at the bottom of the parent storm, 00:02:55.412 --> 00:02:58.990 it sucks it in and turns it into a rotating wall of cloud, 00:02:58.990 --> 00:03:02.826 forming a link between the storm that created it and the Earth. 00:03:02.826 --> 00:03:05.406 The second that tube of spinning cloud touches the ground, 00:03:05.406 --> 00:03:07.628 it becomes a tornado. 00:03:07.628 --> 00:03:13.359 Most are small and short-lived, producing winds of 65-110 miles per hour, 00:03:13.359 --> 00:03:18.609 but others can last for over an hour, producing 200 mile per hour winds. 00:03:18.609 --> 00:03:21.030 They are beautiful but terrifying, 00:03:21.030 --> 00:03:24.335 especially if you or your town is in its path. 00:03:24.335 --> 00:03:27.700 In that case, no one, not even tornado chasers like me, 00:03:27.700 --> 00:03:30.765 enjoy watching thing unfold. 00:03:30.765 --> 00:03:34.578 Just like everything, however, tornadoes do come to an end. 00:03:34.578 --> 00:03:38.266 When the temperature difference disappears and conditions grow more stable, 00:03:38.266 --> 00:03:40.214 or the moisture in the air dries up, 00:03:40.214 --> 00:03:45.641 the once fierce parent storm loses momentum and draws its tornado back inside. 00:03:45.641 --> 00:03:50.485 Even so, meteorologists and storm chasers like me will remain on the lookout, 00:03:50.485 --> 00:03:55.800 watching, always watching to see if the storm releases its long rope again.