1 00:00:01,068 --> 00:00:03,269 Viewers like you make this program possible. 2 00:00:03,270 --> 00:00:05,339 Support your local PBS station. 3 00:00:16,817 --> 00:00:20,253 {\an8}A freakish kind of weather event... 4 00:00:20,254 --> 00:00:21,721 {\an8}We should not be here. 5 00:00:21,722 --> 00:00:23,456 {\an8}I know. I'm shaking right now. 6 00:00:23,457 --> 00:00:27,060 {\an8}...is now striking again and again. 7 00:00:27,061 --> 00:00:28,061 {\an8}People were panicking, 8 00:00:28,062 --> 00:00:29,529 {\an8}running, taking cover. 9 00:00:29,530 --> 00:00:31,164 {\an8}Intense... 10 00:00:31,165 --> 00:00:32,432 {\an8}Batten down the hatches 11 00:00:32,433 --> 00:00:35,301 {\an8}for the potential for straight-line wind gusts 12 00:00:35,302 --> 00:00:38,338 {\an8}in excess of 75 miles an hour. 13 00:00:39,673 --> 00:00:41,574 {\an8}Highly localized. 14 00:00:41,575 --> 00:00:43,743 {\an8}That thing just collapsed right on those mountains 15 00:00:43,744 --> 00:00:45,945 and all that air is just exploding. 16 00:00:47,281 --> 00:00:49,682 And devastating. 17 00:00:49,683 --> 00:00:51,951 MAN Get away from the glass! 18 00:00:51,952 --> 00:00:53,686 It sucked windows out. 19 00:00:53,687 --> 00:00:56,122 There was glass everywhere. 20 00:00:56,123 --> 00:00:59,560 {\an8}They fall from the sky without warning. 21 00:01:02,396 --> 00:01:05,064 {\an8}Explosions of wind and water so violent, 22 00:01:05,065 --> 00:01:08,635 {\an8}they can flatten homes in seconds. 23 00:01:08,636 --> 00:01:12,439 {\an8}They're known as rain bombs. 24 00:01:12,440 --> 00:01:15,575 {\an8}And they're getting stronger. 25 00:01:15,576 --> 00:01:17,243 The damage each year just continues 26 00:01:17,244 --> 00:01:18,778 to pile up and up and up. 27 00:01:18,779 --> 00:01:22,182 Now researchers are attempting to understand 28 00:01:22,183 --> 00:01:23,917 these destructive weather events. 29 00:01:25,219 --> 00:01:28,021 In some cases, it can look like a bomb went off. 30 00:01:28,022 --> 00:01:32,192 Trying to predict where they'll drop and when. 31 00:01:32,193 --> 00:01:35,695 It's not safe to be outside-- you've got about 20 minutes 32 00:01:35,696 --> 00:01:38,032 until this severe storm passes through. 33 00:01:40,301 --> 00:01:42,202 {\an8}"Rain Bombs." 34 00:01:42,203 --> 00:01:44,705 {\an8}Right now, on "NOVA." 35 00:02:09,096 --> 00:02:11,931 August 2011. 36 00:02:11,932 --> 00:02:13,934 The Pukkelpop Music Festival, Belgium. 37 00:02:15,169 --> 00:02:17,470 Out of nowhere, the skies darken... 38 00:02:20,007 --> 00:02:24,143 ...as powerful winds gust at over 80 miles per hour. 39 00:02:24,144 --> 00:02:27,480 MAN Please exit the tent! 40 00:02:27,481 --> 00:02:29,782 Stages collapse. 41 00:02:29,783 --> 00:02:31,684 {\an8}Very quickly, within a couple of minutes, 42 00:02:31,685 --> 00:02:33,720 {\an8}it became probably the heaviest rain I'd ever seen. 43 00:02:33,721 --> 00:02:37,223 {\an8}Lauren Beehan was 19 when she and her friends 44 00:02:37,224 --> 00:02:40,194 {\an8}traveled from Ireland to Belgium for the festival. 45 00:02:42,897 --> 00:02:44,831 {\an8}You couldn't see anything, really. 46 00:02:44,832 --> 00:02:47,967 {\an8}There was wind blowing debris. 47 00:02:47,968 --> 00:02:50,370 It was very much a case of feeling like we were trapped. 48 00:02:52,473 --> 00:02:55,808 For it to turn from such a sunny, cloudless day 49 00:02:55,809 --> 00:02:59,145 to something apocalyptic in the space of 20 minutes 50 00:02:59,146 --> 00:03:00,713 is frightening. 51 00:03:00,714 --> 00:03:02,682 It's like something from a disaster movie. 52 00:03:02,683 --> 00:03:06,252 140 people are injured 53 00:03:06,253 --> 00:03:10,590 and five festivalgoers lose their lives. 54 00:03:13,093 --> 00:03:15,161 August 2024. 55 00:03:15,162 --> 00:03:16,930 A super-yacht called the Bayesian 56 00:03:16,931 --> 00:03:19,666 sinks off the coast of Sicily. 57 00:03:20,768 --> 00:03:23,503 CCTV from the shore that night 58 00:03:23,504 --> 00:03:26,306 catches the vessel's mast, lights barely visible, 59 00:03:26,307 --> 00:03:29,543 in the 100-mile-per-hour wind gusts and rain. 60 00:03:31,478 --> 00:03:34,515 It drags anchor, then capsizes. 61 00:03:36,517 --> 00:03:39,553 Divers recover seven bodies from the wreckage. 62 00:03:44,491 --> 00:03:46,260 July 2018. 63 00:03:47,661 --> 00:03:50,863 In heavy rain at Durango International Airport, 64 00:03:50,864 --> 00:03:55,603 Aeroméxico Connect Flight 2431 is cleared for takeoff. 65 00:04:03,310 --> 00:04:04,778 Jesus ! 66 00:04:07,514 --> 00:04:09,682 {\an8}No sabemos si fue un rayo 67 00:04:09,683 --> 00:04:12,619 {\an8}o un problema mecánico. 68 00:04:12,620 --> 00:04:15,555 The aircraft crashes back down to Earth 69 00:04:15,556 --> 00:04:17,957 before it even clears the runway. 70 00:04:17,958 --> 00:04:21,562 Miraculously, there are no fatalities. 71 00:04:26,500 --> 00:04:28,635 {\an8}Each of these events was caused 72 00:04:28,636 --> 00:04:30,570 {\an8}by a mysterious weather phenomenon, 73 00:04:30,571 --> 00:04:33,539 {\an8}recognized only in the last 50 years. 74 00:04:36,210 --> 00:04:38,311 {\an8}Each began with a thunderstorm, 75 00:04:38,312 --> 00:04:42,516 {\an8}but what followed was much more violent and unexpected. 76 00:04:45,252 --> 00:04:50,123 {\an8}Highly localized, sudden, and extreme rainfall 77 00:04:50,124 --> 00:04:52,893 {\an8}and low-altitude, high-speed winds. 78 00:04:54,428 --> 00:04:56,596 {\an8}They're nicknamed rain bombs, 79 00:04:56,597 --> 00:05:00,066 {\an8}but scientists call them downbursts. 80 00:05:00,067 --> 00:05:02,068 {\an8}So, what are they? 81 00:05:02,069 --> 00:05:04,271 {\an8}And what causes them? 82 00:05:18,085 --> 00:05:19,819 Mike Olbinski 83 00:05:19,820 --> 00:05:22,990 is one of the world's foremost thunderstorm photographers. 84 00:05:24,458 --> 00:05:27,527 After 15 years of chasing storms, 85 00:05:27,528 --> 00:05:29,395 he's mastered the art of being 86 00:05:29,396 --> 00:05:31,531 in exactly the right spot at the right time 87 00:05:31,532 --> 00:05:34,435 to photograph an elusive weather phenomenon. 88 00:05:36,003 --> 00:05:39,139 Rain bombs exploding from the sky. 89 00:05:40,374 --> 00:05:43,409 His images can help scientists understand 90 00:05:43,410 --> 00:05:45,611 how these weather systems form 91 00:05:45,612 --> 00:05:48,581 and how they detonate. 92 00:05:48,582 --> 00:05:51,918 {\an8}We have an updraft going up right to our west, 93 00:05:51,919 --> 00:05:55,588 and then this big storm is forming right behind it, 94 00:05:55,589 --> 00:05:57,223 and I can see it on the horizon, 95 00:05:57,224 --> 00:06:00,693 so I think we need to get a little bit more west. 96 00:06:08,469 --> 00:06:10,770 {\an8}Growing up in Phoenix, 97 00:06:10,771 --> 00:06:13,439 {\an8}we used to watch lightning storms, you know, 98 00:06:13,440 --> 00:06:15,341 {\an8}outside at night. 99 00:06:15,342 --> 00:06:18,945 {\an8}I loved them, and I've always loved them, 100 00:06:18,946 --> 00:06:20,580 {\an8}and I traced it back 101 00:06:20,581 --> 00:06:22,381 {\an8}to seeing a lightning bolt strike behind my house. 102 00:06:22,382 --> 00:06:26,253 {\an8}I still have this insane, vivid memory of it happening. 103 00:06:27,621 --> 00:06:30,324 {\an8}Mike is on the hunt for rain bombs. 104 00:06:31,291 --> 00:06:33,326 {\an8}These intense weather events are striking 105 00:06:33,327 --> 00:06:35,229 {\an8}with greater strength than ever. 106 00:06:36,530 --> 00:06:38,798 To track one down, he first needs to find 107 00:06:38,799 --> 00:06:40,800 a developing thunderstorm. 108 00:06:44,204 --> 00:06:46,072 But what is the difference 109 00:06:46,073 --> 00:06:49,109 between a rain bomb and a run-of-the-mill thunderstorm? 110 00:06:51,378 --> 00:06:52,879 In a normal thunderstorm, 111 00:06:52,880 --> 00:06:56,115 {\an8}you get heavy rainfall, lightning, and sometimes hail. 112 00:06:56,116 --> 00:06:59,353 {\an8}And this can happen over hours. 113 00:07:00,420 --> 00:07:04,090 {\an8}A thunderstorm can drop rain at about two inches per hour. 114 00:07:04,091 --> 00:07:07,327 {\an8}A rain bomb can triple that rate. 115 00:07:09,696 --> 00:07:11,898 {\an8}And in a rain bomb, 116 00:07:11,899 --> 00:07:15,201 {\an8}the rain and hail aren't just falling to the ground. 117 00:07:15,202 --> 00:07:19,139 {\an8}They're being thrown down by hurricane-force vertical winds. 118 00:07:20,240 --> 00:07:22,809 {\an8}What does a rain bomb look like? 119 00:07:22,810 --> 00:07:24,577 {\an8}It looks a massive volume 120 00:07:24,578 --> 00:07:26,412 {\an8}of rain and cold air 121 00:07:26,413 --> 00:07:28,915 {\an8}coming from cloud base to the surface. 122 00:07:38,592 --> 00:07:40,793 Across the planet, 123 00:07:40,794 --> 00:07:42,328 there are 2,000 electrical storms 124 00:07:42,329 --> 00:07:43,896 generating thunder and lightning 125 00:07:43,897 --> 00:07:45,731 at any given moment. 126 00:07:47,301 --> 00:07:50,269 {\an8}Each one of them releases more energy over its lifetime 127 00:07:50,270 --> 00:07:55,242 {\an8}than the 15-kiloton atomic bomb dropped on Hiroshima. 128 00:07:56,910 --> 00:08:00,012 {\an8}Every rain bomb forms from a developing thunderstorm, 129 00:08:00,013 --> 00:08:02,315 {\an8}but to understand how, 130 00:08:02,316 --> 00:08:05,552 {\an8}we must first understand how clouds form. 131 00:08:11,892 --> 00:08:15,228 When sunlight hits the Earth, the surface heats up, 132 00:08:15,229 --> 00:08:18,865 and water from oceans, lakes, soils, and plants 133 00:08:18,866 --> 00:08:22,469 starts to evaporate, turning into water vapor. 134 00:08:24,504 --> 00:08:28,976 {\an8}That water vapor and the warm air around it start to rise. 135 00:08:30,777 --> 00:08:32,745 {\an8}As it starts to rise, 136 00:08:32,746 --> 00:08:36,382 {\an8}it takes all of the water vapor near the surface of the Earth 137 00:08:36,383 --> 00:08:38,085 {\an8}up into the atmosphere. 138 00:08:39,419 --> 00:08:43,457 {\an8}As it lifts that up in the air, that parcel of air cools. 139 00:08:45,092 --> 00:08:46,492 {\an8}The colder the parcel, 140 00:08:46,493 --> 00:08:47,927 {\an8}the less able it is 141 00:08:47,928 --> 00:08:50,129 {\an8}to carry around that water vapor, 142 00:08:50,130 --> 00:08:55,335 {\an8}and so it forces it out into the formation of cloud droplets. 143 00:08:56,436 --> 00:08:58,871 {\an8}Clouds form where the water vapor condenses 144 00:08:58,872 --> 00:09:02,041 {\an8}into tiny water droplets, so small and light 145 00:09:02,042 --> 00:09:05,913 {\an8}that they stay aloft, instead of falling as rain. 146 00:09:07,581 --> 00:09:11,051 {\an8}The altitude where this happens is called the cloud base. 147 00:09:12,219 --> 00:09:15,121 {\an8}You see lots of little clouds developing, 148 00:09:15,122 --> 00:09:17,924 {\an8}and they all have the same cloud base. 149 00:09:17,925 --> 00:09:20,726 So the cloud bases are actually occurring 150 00:09:20,727 --> 00:09:24,364 at the same temperature, and hence the same height. 151 00:09:29,536 --> 00:09:33,006 In Arizona, the summer monsoon season has arrived. 152 00:09:34,007 --> 00:09:37,076 It carries moist, warm air from the Gulf of California, 153 00:09:37,077 --> 00:09:40,981 the perfect fuel for thunderstorms and rain bombs. 154 00:09:42,249 --> 00:09:43,883 We can feel it in the air, 155 00:09:43,884 --> 00:09:46,152 that it's really humid out, there's moisture, 156 00:09:46,153 --> 00:09:49,055 it's warm, so we've got the environment 157 00:09:49,056 --> 00:09:50,222 for, for storms to form. 158 00:09:50,223 --> 00:09:53,559 We're seeing these strong 159 00:09:53,560 --> 00:09:55,628 cauliflower kind of shape to the top. 160 00:09:55,629 --> 00:09:57,830 When you're seeing that, 161 00:09:57,831 --> 00:09:59,966 you've got to imagine how intense that is 162 00:09:59,967 --> 00:10:03,736 to go from nothing to this sharply defined cloud. 163 00:10:03,737 --> 00:10:05,304 And then a couple of them get a little bigger, 164 00:10:05,305 --> 00:10:08,007 and then you get something like this, where, boom, it erupts. 165 00:10:11,011 --> 00:10:13,012 If the conditions are right, 166 00:10:13,013 --> 00:10:16,182 these simple clouds can turn into thunderstorms. 167 00:10:16,183 --> 00:10:17,850 When you have 168 00:10:17,851 --> 00:10:20,252 these puffy, fluffy clouds that you see in the sky, 169 00:10:20,253 --> 00:10:23,389 {\an8}there are some interesting things going on inside. 170 00:10:23,390 --> 00:10:25,191 {\an8}Condensation is happening, 171 00:10:25,192 --> 00:10:27,293 {\an8}and heat is actually being released 172 00:10:27,294 --> 00:10:29,496 {\an8}as water vapor is changing to water. 173 00:10:31,765 --> 00:10:33,632 {\an8}As the water vapor cools, 174 00:10:33,633 --> 00:10:35,368 {\an8}it condenses into droplets 175 00:10:35,369 --> 00:10:38,105 {\an8}that form a cloud, warming the surrounding air. 176 00:10:39,940 --> 00:10:43,676 The now-warmer air rises, creating more updraft, 177 00:10:43,677 --> 00:10:46,579 lifting more air higher into the cooler atmosphere, 178 00:10:46,580 --> 00:10:49,648 where even more water can condense, 179 00:10:49,649 --> 00:10:51,885 which further warms the air. 180 00:10:53,520 --> 00:10:55,321 If the conditions are right, 181 00:10:55,322 --> 00:10:58,591 with enough moisture rising into cold air above, 182 00:10:58,592 --> 00:11:00,860 this fuels a positive feedback loop 183 00:11:00,861 --> 00:11:03,864 that intensifies the cloud's growth. 184 00:11:13,206 --> 00:11:16,442 I see, like, a whole line of updrafts going up, 185 00:11:16,443 --> 00:11:18,411 so I like that. 186 00:11:18,412 --> 00:11:21,547 A lot of these tops today, they just look 187 00:11:21,548 --> 00:11:23,849 really strong. 188 00:11:23,850 --> 00:11:25,751 Sometimes you got the towers going up, 189 00:11:25,752 --> 00:11:28,120 but they don't have the same kind of powerful look. 190 00:11:28,121 --> 00:11:29,822 They're bubbly like a cauliflower, 191 00:11:29,823 --> 00:11:31,924 but they're just a little less intense. 192 00:11:31,925 --> 00:11:34,293 Well, a couple of these, if you look at them, 193 00:11:34,294 --> 00:11:37,063 they just look like there's so many areas 194 00:11:37,064 --> 00:11:39,098 where it's just knuckle-y 195 00:11:39,099 --> 00:11:40,967 and explosive-looking. 196 00:11:42,269 --> 00:11:44,370 Oh! I just saw two big bolts strike 197 00:11:44,371 --> 00:11:47,007 way out there on the horizon-- whew! 198 00:11:51,344 --> 00:11:53,112 But I think something big's going to happen here. 199 00:11:53,113 --> 00:11:55,848 It's a nice, large, dark area. 200 00:11:55,849 --> 00:11:58,484 This is probably going to turn into a really strong storm. 201 00:11:58,485 --> 00:12:00,619 I would expect, I would hope. 202 00:12:00,620 --> 00:12:03,689 I'm trying to catch some lightning right now. 203 00:12:03,690 --> 00:12:05,458 I'm doing two timelapses. 204 00:12:05,459 --> 00:12:06,859 Lightning is an indicator 205 00:12:06,860 --> 00:12:10,931 that the updraft is tall enough to have ice and hail. 206 00:12:15,735 --> 00:12:18,003 {\an8}Ice and hail are key ingredients 207 00:12:18,004 --> 00:12:20,740 {\an8}that drive the most powerful rain bombs. 208 00:12:21,875 --> 00:12:25,544 But how does something as solid as ice or hail form 209 00:12:25,545 --> 00:12:28,314 and stay aloft in the atmosphere? 210 00:12:28,315 --> 00:12:30,916 When water vapor condenses in clouds, 211 00:12:30,917 --> 00:12:34,386 it releases an extraordinary amount of energy. 212 00:12:34,387 --> 00:12:36,856 That makes our clouds very turbulent 213 00:12:36,857 --> 00:12:40,159 {\an8}and that lifts the air higher up in the cloud. 214 00:12:40,160 --> 00:12:41,794 {\an8}At some point in time, 215 00:12:41,795 --> 00:12:45,197 that air will cross over what we call the freezing level 216 00:12:45,198 --> 00:12:49,001 to form things like snowflakes and hailstones, 217 00:12:49,002 --> 00:12:51,237 and that change in phase, of course, 218 00:12:51,238 --> 00:12:53,540 releases more energy. 219 00:12:55,308 --> 00:12:57,309 This energy, in the form of heat, 220 00:12:57,310 --> 00:13:00,880 drives the further growth of the cloud, expanding upward 221 00:13:00,881 --> 00:13:03,482 to the very top of the troposphere, 222 00:13:03,483 --> 00:13:06,853 up to 12 miles above ground level. 223 00:13:08,255 --> 00:13:11,090 Above the troposphere sits a warmer band of air 224 00:13:11,091 --> 00:13:13,225 called the stratosphere. 225 00:13:13,226 --> 00:13:16,562 This warm air acts as a lid preventing the cloud 226 00:13:16,563 --> 00:13:19,698 from climbing any higher, so it spreads out flat, 227 00:13:19,699 --> 00:13:22,369 forming a distinctive anvil shape. 228 00:13:24,104 --> 00:13:26,105 So we've gone from the development 229 00:13:26,106 --> 00:13:27,940 of a tiny little fluffy cloud 230 00:13:27,941 --> 00:13:31,443 to these very tall, extensive storms 231 00:13:31,444 --> 00:13:33,179 that are now carrying around 232 00:13:33,180 --> 00:13:37,183 large amounts of hailstones and snowflakes. 233 00:13:37,184 --> 00:13:40,386 This storm is now seriously ready to do business. 234 00:13:42,589 --> 00:13:44,757 {\an8}Lightning bolts are a telltale sign 235 00:13:44,758 --> 00:13:47,826 {\an8}that a cloud has developed into a thunderstorm. 236 00:13:49,262 --> 00:13:50,629 {\an8}Raindrops get so big, 237 00:13:50,630 --> 00:13:53,299 {\an8}they're too heavy to be held by the cloud's updraft, 238 00:13:53,300 --> 00:13:56,402 {\an8}and so it begins to rain. 239 00:13:56,403 --> 00:13:58,904 {\an8}Or, if conditions are right, it can go on to develop 240 00:13:58,905 --> 00:14:01,274 {\an8}into a violent rain bomb. 241 00:14:04,744 --> 00:14:07,146 {\an8}To understand why some thunderstorms 242 00:14:07,147 --> 00:14:08,948 {\an8}collapse into rain bombs, 243 00:14:08,949 --> 00:14:12,519 {\an8}it helps to know what's going on inside that rain cloud. 244 00:14:14,054 --> 00:14:15,354 {\an8}One way to uncover that 245 00:14:15,355 --> 00:14:18,991 {\an8}is to analyze the stuff that falls out. 246 00:14:18,992 --> 00:14:24,264 {\an8}Particularly hailstones, icy chunks of frozen cloud. 247 00:14:32,505 --> 00:14:34,306 {\an8}Over the summer of 2025, 248 00:14:34,307 --> 00:14:38,544 {\an8}storm researchers teamed up on a project called ICECHIP 249 00:14:38,545 --> 00:14:40,145 {\an8}to collect hailstones 250 00:14:40,146 --> 00:14:43,148 {\an8}from thunderstorms striking the Great Plains. 251 00:14:43,149 --> 00:14:45,150 {\an8}BECKY ADAMS-SELIN: The ground teams, 252 00:14:45,151 --> 00:14:47,586 {\an8}the teams looking at what kind of hail fell at the surface, 253 00:14:47,587 --> 00:14:50,122 {\an8}is really what made this campaign unique, 254 00:14:50,123 --> 00:14:52,091 {\an8}because other campaigns, you know, 255 00:14:52,092 --> 00:14:54,660 {\an8}would go and, and look at, at storms with mobile radars, 256 00:14:54,661 --> 00:14:56,362 {\an8}and that's a lot of great information, 257 00:14:56,363 --> 00:15:00,699 {\an8}but only ours also tried to really fully characterize 258 00:15:00,700 --> 00:15:02,769 {\an8}what kind of hail was down at the surface. 259 00:15:09,542 --> 00:15:11,510 {\an8}The ICECHIP team brings the hailstones 260 00:15:11,511 --> 00:15:14,247 {\an8}to a cold lab in Boulder, Colorado. 261 00:15:17,050 --> 00:15:20,352 Here, at below-freezing temperatures, 262 00:15:20,353 --> 00:15:22,221 atmospheric scientists Anthony Bernal Ayala 263 00:15:22,222 --> 00:15:24,023 and Becky Adams-Selin 264 00:15:24,024 --> 00:15:27,160 process and analyze each of the thousands of samples. 265 00:15:28,428 --> 00:15:30,429 Large hailstones are extremely valuable 266 00:15:30,430 --> 00:15:32,998 in understanding more about the thunderstorm they came from. 267 00:15:35,769 --> 00:15:37,970 {\an8}Once you get the hailstone, you can actually just go ahead 268 00:15:37,971 --> 00:15:40,372 {\an8}and cut a thin slice out of it. 269 00:15:40,373 --> 00:15:44,076 {\an8}And you polish it up so it's an even thickness. 270 00:15:44,077 --> 00:15:47,112 {\an8}You can get a lot of information just by looking at the slice. 271 00:15:47,113 --> 00:15:50,616 {\an8}You can see different rings in the hail, 272 00:15:50,617 --> 00:15:51,884 {\an8}and much like tree rings, 273 00:15:51,885 --> 00:15:53,752 {\an8}those represent different conditions 274 00:15:53,753 --> 00:15:56,222 {\an8}under which the hail was growing in the storm. 275 00:15:57,190 --> 00:15:58,590 {\an8}When we look at hailstones 276 00:15:58,591 --> 00:15:59,758 {\an8}and we look at the cross-section, 277 00:15:59,759 --> 00:16:01,560 {\an8}one of the things that we look at 278 00:16:01,561 --> 00:16:03,295 {\an8}is whether the layer is opaque 279 00:16:03,296 --> 00:16:05,164 {\an8}or whether layer is clear. 280 00:16:05,165 --> 00:16:07,166 {\an8}When you look at that clear layer, 281 00:16:07,167 --> 00:16:10,402 {\an8}you're looking at where there is warmer sub-zero temperatures, 282 00:16:10,403 --> 00:16:12,304 {\an8}so it's a little bit warmer in the cloud, 283 00:16:12,305 --> 00:16:14,506 {\an8}where liquid water freezes slowly, 284 00:16:14,507 --> 00:16:16,508 {\an8}and because this freezes slowly, 285 00:16:16,509 --> 00:16:18,644 {\an8}that allowed the air bubbles to escape. 286 00:16:18,645 --> 00:16:20,346 {\an8}So it's gonna be clear-- there's not gonna be a lot 287 00:16:20,347 --> 00:16:22,314 {\an8}of air bubbles trapped in this layer. 288 00:16:22,315 --> 00:16:24,283 {\an8}When you look at the opaque layer, 289 00:16:24,284 --> 00:16:27,286 {\an8}because it's in temperatures in the cloud that are very cold, 290 00:16:27,287 --> 00:16:29,488 it's gonna freeze very rapidly. 291 00:16:29,489 --> 00:16:31,290 So, because it freezes very rapidly, 292 00:16:31,291 --> 00:16:34,193 it actually traps a lot of air bubbles in that layer, 293 00:16:34,194 --> 00:16:35,862 so that it actually looks opaque. 294 00:16:36,863 --> 00:16:38,864 But why would a single hailstone 295 00:16:38,865 --> 00:16:41,800 have both clear and opaque layers? 296 00:16:41,801 --> 00:16:45,271 And what does that reveal about how the hailstone formed? 297 00:16:46,373 --> 00:16:48,073 The hailstone had to have been moving around in the storm 298 00:16:48,074 --> 00:16:49,875 to experience these different conditions 299 00:16:49,876 --> 00:16:53,011 and to create the different layers. 300 00:16:53,012 --> 00:16:56,448 We think that it's actually rotating somehow 301 00:16:56,449 --> 00:16:57,983 around the updraft 302 00:16:57,984 --> 00:16:59,985 to accumulate all those layers 303 00:16:59,986 --> 00:17:01,788 that we see in the cross-section. 304 00:17:02,889 --> 00:17:04,723 {\an8}These layers are evidence 305 00:17:04,724 --> 00:17:08,160 {\an8}that the hailstones are continually rising and falling 306 00:17:08,161 --> 00:17:10,829 {\an8}inside a developing thundercloud. 307 00:17:10,830 --> 00:17:13,665 {\an8}This hailstone spent most of its time 308 00:17:13,666 --> 00:17:16,735 in very cold temperatures in the cloud, 309 00:17:16,736 --> 00:17:18,537 but for a very short period, 310 00:17:18,538 --> 00:17:21,740 it actually went through a warmer side of the cloud. 311 00:17:21,741 --> 00:17:23,542 Then it went back, a very cold temperature, 312 00:17:23,543 --> 00:17:25,978 then it went back, a warmer section of the cloud, 313 00:17:25,979 --> 00:17:28,815 where it probably fell and then it was collected at the surface. 314 00:17:30,316 --> 00:17:32,084 To grow to two inches wide, 315 00:17:32,085 --> 00:17:35,487 this hailstone most likely spent over half an hour 316 00:17:35,488 --> 00:17:38,257 being lifted and dropped inside the storm. 317 00:17:39,659 --> 00:17:42,161 {\an8}There's updrafts, there's downdrafts. 318 00:17:42,162 --> 00:17:43,695 {\an8}There could be hail. 319 00:17:43,696 --> 00:17:45,697 {\an8}There could be circulations or rotations 320 00:17:45,698 --> 00:17:47,266 {\an8}inside that cloud. 321 00:17:47,267 --> 00:17:50,869 {\an8}These intense storms are very turbulent. 322 00:17:50,870 --> 00:17:54,173 {\an8}They have regions where air is rising very rapidly, 323 00:17:54,174 --> 00:17:57,743 sometimes at speeds of 150 miles per hour. 324 00:18:00,146 --> 00:18:04,783 This mixing of hail and ice provides the energy necessary 325 00:18:04,784 --> 00:18:07,453 for the storm to produce thunder and lightning. 326 00:18:09,722 --> 00:18:11,190 In mature thunderstorms, 327 00:18:11,191 --> 00:18:13,725 like the one that made Anthony's hailstone, 328 00:18:13,726 --> 00:18:15,661 immensely powerful updrafts 329 00:18:15,662 --> 00:18:19,231 can suspend over a million tons of hail 330 00:18:19,232 --> 00:18:21,366 miles above the ground. 331 00:18:21,367 --> 00:18:23,335 It's actually quite incredible 332 00:18:23,336 --> 00:18:25,437 that storms are able to suspend 333 00:18:25,438 --> 00:18:28,874 this large mass of liquid raindrops 334 00:18:28,875 --> 00:18:31,977 and other ice, like hail and snowflakes, 335 00:18:31,978 --> 00:18:34,013 so high up in the atmosphere. 336 00:18:35,815 --> 00:18:39,084 {\an8}What happens to this core of rain, hail, and ice 337 00:18:39,085 --> 00:18:41,053 {\an8}determines whether the storm remains 338 00:18:41,054 --> 00:18:43,288 {\an8}a regular thunderstorm 339 00:18:43,289 --> 00:18:46,692 {\an8}or unleashes a rain bomb. 340 00:18:52,332 --> 00:18:54,867 {\an8}Dude, that looks freaking awesome. 341 00:18:54,868 --> 00:18:58,237 {\an8}That's just plummeting-- that's, like, a downburst happening. 342 00:18:58,238 --> 00:19:01,707 {\an8}When you see that middle rain shaft area, 343 00:19:01,708 --> 00:19:02,774 {\an8}where it looks like a blob, 344 00:19:02,775 --> 00:19:04,643 {\an8}that's usually a good telltale sign 345 00:19:04,644 --> 00:19:06,212 {\an8}of a downburst happening. 346 00:19:07,247 --> 00:19:08,480 Oh, man. 347 00:19:08,481 --> 00:19:09,949 This is stunning. 348 00:19:13,987 --> 00:19:16,154 {\an8}In a fully developed thunderstorm cloud, 349 00:19:16,155 --> 00:19:19,192 {\an8}what goes up must eventually come down. 350 00:19:20,260 --> 00:19:23,328 {\an8}The cloud's updraft begins to peter out 351 00:19:23,329 --> 00:19:26,532 {\an8}as rising air cools and sinks back toward the ground 352 00:19:26,533 --> 00:19:28,234 {\an8}as a downdraft. 353 00:19:29,469 --> 00:19:32,472 {\an8}This is what happens in a standard thunderstorm. 354 00:19:35,141 --> 00:19:37,643 {\an8}But in a rain bomb, things are different. 355 00:19:37,644 --> 00:19:39,144 {\an8}Because in a rain bomb, 356 00:19:39,145 --> 00:19:42,014 {\an8}a sudden, extremely strong downdraft 357 00:19:42,015 --> 00:19:44,383 {\an8}overwhelms the updraft, 358 00:19:44,384 --> 00:19:47,819 {\an8}causing the cloud's core of ice and hail to collapse 359 00:19:47,820 --> 00:19:49,388 {\an8}all at once. 360 00:19:49,389 --> 00:19:53,560 {\an8}Two processes drive this sudden downdraft intensification. 361 00:19:54,694 --> 00:19:58,363 {\an8}The first is that, as the rain and hail start to fall downward, 362 00:19:58,364 --> 00:20:00,198 {\an8}they drag on the air. 363 00:20:00,199 --> 00:20:02,634 {\an8}So they pull the air down toward the Earth. 364 00:20:05,471 --> 00:20:09,174 {\an8}When massive amounts of rain and hail begin to fall, 365 00:20:09,175 --> 00:20:11,577 {\an8}they help generate a downward rush of air, 366 00:20:11,578 --> 00:20:14,614 {\an8}which can act as the rain bomb's trigger. 367 00:20:15,748 --> 00:20:17,749 {\an8}But that's not all that's required 368 00:20:17,750 --> 00:20:20,385 {\an8}to get a rain bomb started. 369 00:20:20,386 --> 00:20:22,988 {\an8}The second, more important process 370 00:20:22,989 --> 00:20:26,158 {\an8}that accelerates this developing downburst toward the ground 371 00:20:26,159 --> 00:20:28,627 {\an8}is evaporation. 372 00:20:28,628 --> 00:20:30,796 Evaporation is a cooling process. 373 00:20:30,797 --> 00:20:32,297 You experience it when you step out 374 00:20:32,298 --> 00:20:33,899 of a swimming pool or your shower. 375 00:20:33,900 --> 00:20:36,802 {\an8}When you've got drops of water on your skin, 376 00:20:36,803 --> 00:20:40,273 {\an8}as these drops evaporate, your skin feels very cold. 377 00:20:41,608 --> 00:20:44,242 If winds blowing into the cloud are dry, 378 00:20:44,243 --> 00:20:46,878 they can rapidly evaporate raindrops, 379 00:20:46,879 --> 00:20:49,748 as well as melt ice and hail. 380 00:20:49,749 --> 00:20:54,253 {\an8}This cools the surrounding air, making it denser and heavier. 381 00:20:56,389 --> 00:21:00,859 {\an8}This very cold air, very dense air, has to sink. 382 00:21:00,860 --> 00:21:03,161 {\an8}So it's going to rush toward the surface, 383 00:21:03,162 --> 00:21:06,299 {\an8}taking all of that large mass of rain and hail. 384 00:21:07,634 --> 00:21:10,502 {\an8}As rain and hail descend from the cloud, 385 00:21:10,503 --> 00:21:12,471 {\an8}if they hit more dry air, 386 00:21:12,472 --> 00:21:15,807 {\an8}the evaporation can accelerate further. 387 00:21:15,808 --> 00:21:19,211 {\an8}As the raindrops fall below cloud base 388 00:21:19,212 --> 00:21:20,679 {\an8}into this drier air, 389 00:21:20,680 --> 00:21:22,814 {\an8}they will evaporate in that location, too. 390 00:21:22,815 --> 00:21:25,984 {\an8}This, of course, is going to really intensifies 391 00:21:25,985 --> 00:21:27,386 {\an8}that cooling process. 392 00:21:27,387 --> 00:21:31,857 {\an8}This very cold, dense air then rushes toward the surface, 393 00:21:31,858 --> 00:21:34,593 {\an8}creating these phenomenal scenarios 394 00:21:34,594 --> 00:21:38,096 {\an8}called downbursts or rain bombs. 395 00:21:42,502 --> 00:21:44,136 {\an8}The downdrafts can intensify 396 00:21:44,137 --> 00:21:46,004 {\an8}into hurricane-force vertical winds, 397 00:21:46,005 --> 00:21:50,442 {\an8}driving the cloud's core of hail, rain, and cold air 398 00:21:50,443 --> 00:21:53,513 {\an8}downward, slamming it into the ground. 399 00:21:54,647 --> 00:21:56,548 {\an8}Sometimes, the downburst's rain 400 00:21:56,549 --> 00:22:00,318 {\an8}can completely evaporate before reaching the ground, 401 00:22:00,319 --> 00:22:03,923 {\an8}creating what scientists call a dry downburst. 402 00:22:05,158 --> 00:22:09,261 {\an8}And all of these downbursts, both wet and dry, 403 00:22:09,262 --> 00:22:11,363 {\an8}can strike in just a few minutes, 404 00:22:11,364 --> 00:22:13,899 {\an8}in a remarkably narrow column, 405 00:22:13,900 --> 00:22:17,036 {\an8}as small as just a couple of hundred yards across. 406 00:22:18,738 --> 00:22:21,039 {\an8}And as our atmosphere warms, 407 00:22:21,040 --> 00:22:23,743 {\an8}they're becoming more and more powerful. 408 00:22:25,111 --> 00:22:27,045 It actually can be quite a frightening moment. 409 00:22:27,046 --> 00:22:28,480 There's a lot going on. 410 00:22:28,481 --> 00:22:32,150 There's lightning, there's hail, there's very heavy rain, 411 00:22:32,151 --> 00:22:33,652 and then, of course, the strong wind. 412 00:22:38,591 --> 00:22:41,059 {\an8}Storm chaser Hank Schyma has been caught 413 00:22:41,060 --> 00:22:42,962 {\an8}under a powerful rain bomb. 414 00:22:44,030 --> 00:22:45,130 {\an8}There was a day 415 00:22:45,131 --> 00:22:47,833 {\an8}where I get slammed by a downburst. 416 00:22:53,072 --> 00:22:55,407 {\an8}The rain really picks up and gets really strong, 417 00:22:55,408 --> 00:22:57,309 {\an8}everything turns white, and then, all of a sudden, 418 00:22:57,310 --> 00:23:00,479 {\an8}I can see that I'm about to drive off the road. 419 00:23:01,581 --> 00:23:03,915 {\an8}You can feel the winds rocking your car, 420 00:23:03,916 --> 00:23:04,916 {\an8}and, and the winds are picking up 421 00:23:04,917 --> 00:23:06,685 {\an8}sand and things in the road, 422 00:23:06,686 --> 00:23:10,422 {\an8}and they're slamming them into your car. 423 00:23:10,423 --> 00:23:13,826 {\an8}It's really terrifying and scary. 424 00:23:20,466 --> 00:23:23,970 {\an8}Strong winds are a key element of downbursts. 425 00:23:25,505 --> 00:23:28,841 {\an8}They slam cold air into the ground at high speed. 426 00:23:30,243 --> 00:23:33,044 {\an8}And this air has to go somewhere. 427 00:23:33,045 --> 00:23:35,380 {\an8}They can't go into the ground, so they spread out 428 00:23:35,381 --> 00:23:37,082 {\an8}horizontally in all directions. 429 00:23:37,083 --> 00:23:40,719 {\an8}So, you see extreme surface winds. 430 00:23:40,720 --> 00:23:42,721 {\an8}Cold air hits the ground 431 00:23:42,722 --> 00:23:46,558 {\an8}and pushes out radially from the heart of the downburst. 432 00:23:46,559 --> 00:23:48,360 {\an8}This outflowing air-- 433 00:23:48,361 --> 00:23:50,862 {\an8}remember, it's very cold, dense air-- 434 00:23:50,863 --> 00:23:53,265 {\an8}we refer to as a cold pool, 435 00:23:53,266 --> 00:23:56,168 {\an8}because it is a cold pool of dense air. 436 00:24:00,173 --> 00:24:04,242 {\an8}These advancing banks of cold air can kick up dust, 437 00:24:04,243 --> 00:24:06,178 {\an8}creating the distinctive dust storms 438 00:24:06,179 --> 00:24:08,780 {\an8}often seen in the American Southwest. 439 00:24:08,781 --> 00:24:12,184 {\an8}Dusty cold pools are called haboobs. 440 00:24:12,185 --> 00:24:15,654 {\an8}And they create all sorts of severe weather, 441 00:24:15,655 --> 00:24:17,923 including visibility issues, 442 00:24:17,924 --> 00:24:21,294 road accidents, and breathing issues. 443 00:24:22,528 --> 00:24:24,896 The dust makes the turbulent gust front 444 00:24:24,897 --> 00:24:26,631 of an advancing cold pool 445 00:24:26,632 --> 00:24:28,400 easy to see. 446 00:24:28,401 --> 00:24:31,269 {\an8}But even when no dust is present, 447 00:24:31,270 --> 00:24:35,974 {\an8}this billowing front of cold air is still there. 448 00:24:35,975 --> 00:24:38,376 {\an8}And it's these fierce straight-line winds 449 00:24:38,377 --> 00:24:40,346 {\an8}that inflict the most damage. 450 00:24:41,714 --> 00:24:43,114 {\an8}These winds are 451 00:24:43,115 --> 00:24:45,750 {\an8}strongest near the surface. 452 00:24:45,751 --> 00:24:48,286 {\an8}If you compare that to something like a hurricane, 453 00:24:48,287 --> 00:24:50,222 {\an8}a lot of the strength in a hurricane 454 00:24:50,223 --> 00:24:52,991 {\an8}exists higher up in the atmosphere. 455 00:24:52,992 --> 00:24:58,029 {\an8}But for downbursts, they occur very close to the surface. 456 00:24:58,030 --> 00:25:00,498 {\an8}Trees will just flap down to the ground, 457 00:25:00,499 --> 00:25:03,001 {\an8}and these wind gusts are so strong 458 00:25:03,002 --> 00:25:05,337 {\an8}that you cannot stand on your own feet anymore. 459 00:25:05,338 --> 00:25:06,872 {\an8}In some cases, it can look 460 00:25:06,873 --> 00:25:08,139 {\an8}like a bomb went off. 461 00:25:08,140 --> 00:25:11,309 {\an8}Literally, that air hits the ground at low levels 462 00:25:11,310 --> 00:25:14,512 {\an8}and spreads out in all directions. 463 00:25:14,513 --> 00:25:18,216 {\an8}Those winds are what we call straight-line winds. 464 00:25:18,217 --> 00:25:20,752 {\an8}They are not turning like a tornado turns. 465 00:25:20,753 --> 00:25:22,254 {\an8}They are following straight lines 466 00:25:22,255 --> 00:25:25,591 {\an8}away from where the downburst hits. 467 00:25:35,334 --> 00:25:37,035 This might explain what happened 468 00:25:37,036 --> 00:25:40,438 to Aeroméxico Connect Flight 2431 469 00:25:40,439 --> 00:25:43,875 when it took off from Durango International Airport, 470 00:25:43,876 --> 00:25:46,344 en route to Mexico City. 471 00:25:46,345 --> 00:25:49,748 The rain, while heavy, was not extreme. 472 00:25:49,749 --> 00:25:51,850 There were storms in the area, 473 00:25:51,851 --> 00:25:54,419 {\an8}but the tower had cleared them for takeoff 474 00:25:54,420 --> 00:25:58,290 {\an8}and had told them that they actually have headwinds, 475 00:25:58,291 --> 00:26:00,926 which would provide them lift for takeoff. 476 00:26:00,927 --> 00:26:06,532 Without realizing it, Flight 2431 flew through a downburst. 477 00:26:07,867 --> 00:26:10,035 In just seconds, the plane experienced 478 00:26:10,036 --> 00:26:14,139 a near 180-degree shift in wind direction. 479 00:26:14,140 --> 00:26:17,175 The plane was about 30 feet off the ground, 480 00:26:17,176 --> 00:26:20,045 a very susceptible time on any takeoff, 481 00:26:20,046 --> 00:26:23,615 and this tailwind, it swung from being an uplift 482 00:26:23,616 --> 00:26:26,117 to a sinking motion. 483 00:26:26,118 --> 00:26:29,054 Without the lift generated by a headwind, 484 00:26:29,055 --> 00:26:32,457 the plane plummeted and crashed into the runway. 485 00:26:54,013 --> 00:26:56,648 Luckily, everyone managed to escape 486 00:26:56,649 --> 00:26:59,018 before the plane was fully engulfed in flames. 487 00:27:00,720 --> 00:27:02,587 This wasn't the first passenger jet 488 00:27:02,588 --> 00:27:05,124 to crash in similar conditions. 489 00:27:07,059 --> 00:27:09,794 June 1975. 490 00:27:09,795 --> 00:27:14,467 {\an8}Eastern Airlines Flight 66 crashed on approach to JFK. 491 00:27:17,203 --> 00:27:18,871 {\an8}August 1985. 492 00:27:20,339 --> 00:27:23,909 {\an8}Delta Flight 191 crashed on approach to Dallas Fort Worth. 493 00:27:26,379 --> 00:27:27,980 {\an8}July 1994. 494 00:27:28,948 --> 00:27:31,983 {\an8}U.S. Air Flight 1016 crashed on approach 495 00:27:31,984 --> 00:27:34,520 {\an8}to Charlotte Douglas International Airport. 496 00:27:38,024 --> 00:27:40,992 Those tragic accidents in the '70s and '80s 497 00:27:40,993 --> 00:27:45,530 led to a lot of very significant research in downbursts, 498 00:27:45,531 --> 00:27:47,699 how they operate, and then subsequently, 499 00:27:47,700 --> 00:27:51,536 the technology that we need to warn pilots. 500 00:27:51,537 --> 00:27:55,540 A lot of the airports in the U.S. 501 00:27:55,541 --> 00:27:57,042 are fitted with these weather radars, 502 00:27:57,043 --> 00:27:59,677 but there are many of the airports around the world 503 00:27:59,678 --> 00:28:01,379 do not have this technology. 504 00:28:01,380 --> 00:28:04,516 Aeroméxico flight would not have taken off 505 00:28:04,517 --> 00:28:06,351 had they been aware of the fact 506 00:28:06,352 --> 00:28:09,121 that they were just about to hit a downburst. 507 00:28:11,791 --> 00:28:13,691 When investigators study the loss 508 00:28:13,692 --> 00:28:16,561 of the supposedly unsinkable Bayesian yacht, 509 00:28:16,562 --> 00:28:20,265 which went down on August 19, 2024, 510 00:28:20,266 --> 00:28:23,268 they discover that before it capsized and sank, 511 00:28:23,269 --> 00:28:26,571 {\an8}it had dragged its anchor around 400 yards 512 00:28:26,572 --> 00:28:29,207 {\an8}in a dead straight line. 513 00:28:29,208 --> 00:28:32,844 The Bayesian was anchored 514 00:28:32,845 --> 00:28:35,847 off the north coast of Sicily. 515 00:28:35,848 --> 00:28:38,683 It was in a bay, it was next to another yacht. 516 00:28:39,985 --> 00:28:42,387 This CCTV footage from a camera onshore 517 00:28:42,388 --> 00:28:43,888 about 600 feet away 518 00:28:43,889 --> 00:28:45,991 reveals the boat in the distance. 519 00:28:47,726 --> 00:28:49,194 What ended up happening was, 520 00:28:49,195 --> 00:28:51,596 as these really strong straight-lined winds 521 00:28:51,597 --> 00:28:52,997 hit these yachts, 522 00:28:52,998 --> 00:28:55,633 they dragged anchor in straight lines. 523 00:28:55,634 --> 00:28:57,802 That indicates it was a straight-lined wind, 524 00:28:57,803 --> 00:29:00,605 as opposed to the kind of rotational wind 525 00:29:00,606 --> 00:29:02,407 {\an8}you would get from a tornado. 526 00:29:02,408 --> 00:29:07,479 {\an8}And it was a very large yacht with a very tall mast 527 00:29:07,480 --> 00:29:08,880 and it would appear 528 00:29:08,881 --> 00:29:11,316 that the downburst and associated cold pool 529 00:29:11,317 --> 00:29:13,184 was actually able to roll it over 530 00:29:13,185 --> 00:29:14,954 beyond its point of stability. 531 00:29:16,155 --> 00:29:18,656 {\an8}The yacht succumbed to the same type 532 00:29:18,657 --> 00:29:20,925 {\an8}of extreme low-altitude, straight-line winds 533 00:29:20,926 --> 00:29:24,130 {\an8}that led to the crash of Flight 2431. 534 00:29:30,736 --> 00:29:34,405 {\an8}At the Pukkelpop Festival in 2011, 535 00:29:34,406 --> 00:29:36,407 {\an8}the hail and howling winds struck an area 536 00:29:36,408 --> 00:29:39,077 {\an8}less than a hundred yards across. 537 00:29:39,078 --> 00:29:42,147 {\an8}This was a very narrow downburst. 538 00:29:42,148 --> 00:29:43,781 {\an8}This is what made it so unusual. 539 00:29:43,782 --> 00:29:45,750 You would normally expect such power 540 00:29:45,751 --> 00:29:47,719 from systems that are larger, 541 00:29:47,720 --> 00:29:49,087 where they can transport 542 00:29:49,088 --> 00:29:52,724 more rain and more hail and more wind to the surface 543 00:29:52,725 --> 00:29:55,193 than in a 100-meter-wide downburst. 544 00:29:55,194 --> 00:29:57,362 So, a really remarkable event. 545 00:29:58,430 --> 00:30:00,498 These real-life tragedies reveal 546 00:30:00,499 --> 00:30:03,701 the destructive potential of powerful rain bombs: 547 00:30:03,702 --> 00:30:08,007 intense, highly localized, and short-lived. 548 00:30:13,078 --> 00:30:16,314 But a storm that hits Houston in May 2024 549 00:30:16,315 --> 00:30:19,350 has all the hallmarks of a downburst, 550 00:30:19,351 --> 00:30:22,720 except that it is much bigger. 551 00:30:22,721 --> 00:30:25,590 It travels around a thousand miles 552 00:30:25,591 --> 00:30:29,027 and it lasts much longer than a single downburst-- 553 00:30:29,028 --> 00:30:31,996 more than 12 hours. 554 00:30:31,997 --> 00:30:34,165 A line of severe thunderstorms 555 00:30:34,166 --> 00:30:36,100 is racing into our Greater Houston area. 556 00:30:36,101 --> 00:30:37,669 You should batten down the hatches 557 00:30:37,670 --> 00:30:40,405 for the potential for straight-line wind gusts 558 00:30:40,406 --> 00:30:44,176 at about 70, 80, to 90 miles an hour. 559 00:30:45,477 --> 00:30:49,314 National Weather Service forecaster Amaryllis Cotto 560 00:30:49,315 --> 00:30:52,016 is on call at the Houston/Galveston office 561 00:30:52,017 --> 00:30:54,886 27 miles southeast of Downtown Houston 562 00:30:54,887 --> 00:30:56,354 when the storm hits. 563 00:30:57,790 --> 00:30:59,524 The storm developed very fast 564 00:30:59,525 --> 00:31:03,861 {\an8}in areas of West-Northwest Texas at around 9:00 a.m., 565 00:31:03,862 --> 00:31:06,331 {\an8}and so we could see how fast it was moving. 566 00:31:06,332 --> 00:31:09,067 It was already affecting the Houston metro area 567 00:31:09,068 --> 00:31:10,969 by around 5:00 to 6:00 p.m. 568 00:31:12,304 --> 00:31:13,938 It's not safe to be outside. 569 00:31:13,939 --> 00:31:16,608 You've got about 20 minutes to get hunkered down 570 00:31:16,609 --> 00:31:19,611 on the first-floor interior room of your home, away from windows. 571 00:31:19,612 --> 00:31:21,412 That's the safest place to be 572 00:31:21,413 --> 00:31:24,549 until this severe storm passes through. 573 00:31:24,550 --> 00:31:26,417 It was devastating Houston. 574 00:31:26,418 --> 00:31:28,686 We had a lot of tree damage. 575 00:31:28,687 --> 00:31:30,789 We had millions of people without power. 576 00:31:31,857 --> 00:31:34,058 {\an8}Hank and Natchaya Schyma 577 00:31:34,059 --> 00:31:36,894 {\an8}are five miles north of downtown when the storm hits. 578 00:31:36,895 --> 00:31:40,732 {\an8}He starts recording the storm from his car. 579 00:31:40,733 --> 00:31:46,871 {\an8}Suddenly, it goes from daylight to darkness, and chaos hits. 580 00:31:49,141 --> 00:31:51,110 Here it comes. 581 00:31:52,745 --> 00:31:54,879 Holy (bleep)! Holy (bleep)! 582 00:31:54,880 --> 00:31:57,182 Yup, hang on, I've got it. 583 00:31:59,618 --> 00:32:01,819 {\an8}Um, we should not be here. 584 00:32:01,820 --> 00:32:04,455 {\an8}I'm shaking right now! 585 00:32:04,456 --> 00:32:07,091 {\an8}HANK SCHYMA You can't see a block in front of you 586 00:32:07,092 --> 00:32:09,894 {\an8}just because of the whitewash of wind and rain, 587 00:32:09,895 --> 00:32:11,296 {\an8}and trees are swaying, 588 00:32:11,297 --> 00:32:13,931 {\an8}and downtown Houston is raining glass, 589 00:32:13,932 --> 00:32:16,901 {\an8}as windows are, are failing all up in the skyscrapers. 590 00:32:16,902 --> 00:32:18,936 {\an8}MAN Move away from the glass! 591 00:32:20,839 --> 00:32:22,540 {\an8}The winds associated with this system 592 00:32:22,541 --> 00:32:24,976 {\an8}were hurricane-force winds in the lower levels. 593 00:32:24,977 --> 00:32:29,747 It sucked windows out-- there was glass everywhere. 594 00:32:29,748 --> 00:32:31,449 And in addition to the sucking motion, 595 00:32:31,450 --> 00:32:32,617 inside the buildings, 596 00:32:32,618 --> 00:32:34,652 the pressure is now higher than outside. 597 00:32:34,653 --> 00:32:37,088 So you get this explosive force 598 00:32:37,089 --> 00:32:40,826 that forces windows and glass out of the buildings. 599 00:32:45,264 --> 00:32:48,167 It's the signature of a rain bomb. 600 00:32:49,168 --> 00:32:52,236 Super-strong ground-level winds shattering 601 00:32:52,237 --> 00:32:54,840 any weak windows along their path. 602 00:32:55,974 --> 00:32:58,443 Telltale signs of straight-line wind damage 603 00:32:58,444 --> 00:33:00,545 are seen all over the city. 604 00:33:00,546 --> 00:33:04,048 They pull down power lines across Houston 605 00:33:04,049 --> 00:33:07,619 and plunge one million people into darkness. 606 00:33:09,054 --> 00:33:11,923 But the Houston storm isn't the size of the storms 607 00:33:11,924 --> 00:33:14,992 that hit Pukkelpop or sank the Bayesian. 608 00:33:14,993 --> 00:33:18,029 It's over 50 miles across 609 00:33:18,030 --> 00:33:20,365 and leaves a path of devastation 610 00:33:20,366 --> 00:33:24,402 across the 10,000-square-mile Houston metro area. 611 00:33:24,403 --> 00:33:28,072 Rain bombs just don't grow this big on their own. 612 00:33:28,073 --> 00:33:31,442 They need to gang together to become this large. 613 00:33:31,443 --> 00:33:33,379 But how? 614 00:33:47,993 --> 00:33:52,263 22 miles northeast of Fort Collins, Colorado. 615 00:33:52,264 --> 00:33:55,400 Atmospheric scientist Sue van den Heever's 20-strong team 616 00:33:55,401 --> 00:33:57,168 is out in the field. 617 00:33:57,169 --> 00:33:58,970 I think the forecasters are keen 618 00:33:58,971 --> 00:34:00,371 to have some surface measurements, 619 00:34:00,372 --> 00:34:02,374 Okay. They are trying to assess the moisture. 620 00:34:04,009 --> 00:34:07,044 Her team deploys drones engineered to withstand 621 00:34:07,045 --> 00:34:08,913 extreme weather. 622 00:34:08,914 --> 00:34:10,081 They measure the outflow winds 623 00:34:10,082 --> 00:34:14,385 when the cold air in a downburst crashes to Earth 624 00:34:14,386 --> 00:34:18,524 and races across the landscape, forming the cold pool. 625 00:34:24,696 --> 00:34:27,332 We've launched what we call the flying curtain. 626 00:34:30,169 --> 00:34:32,838 And we're flying a wall of six drones. 627 00:34:34,239 --> 00:34:35,640 We have a lower level of drones 628 00:34:35,641 --> 00:34:37,708 and an upper level of drones. 629 00:34:37,709 --> 00:34:39,510 We have a lot of instruments 630 00:34:39,511 --> 00:34:40,812 that can measure the temperature, 631 00:34:40,813 --> 00:34:42,313 the moisture of the atmosphere. 632 00:34:42,314 --> 00:34:44,983 We've got anemometers on there that can measure the winds. 633 00:34:46,385 --> 00:34:49,220 And this allows us to make measurements of the variability 634 00:34:49,221 --> 00:34:50,321 of the atmosphere, 635 00:34:50,322 --> 00:34:51,622 and as the cold pool advances on us 636 00:34:51,623 --> 00:34:52,824 and blows through us, 637 00:34:52,825 --> 00:34:54,425 we are able to make 638 00:34:54,426 --> 00:34:56,093 that measurement in time, as well. 639 00:34:56,094 --> 00:34:57,428 So there's a lot 640 00:34:57,429 --> 00:35:00,298 that we are characterizing about these cold pools. 641 00:35:02,134 --> 00:35:03,401 Sue and her team 642 00:35:03,402 --> 00:35:06,504 are tracking a storm a safe distance away, 643 00:35:06,505 --> 00:35:07,739 beyond the horizon. 644 00:35:09,541 --> 00:35:13,779 Radar shows that it has produced a downburst of intense rainfall. 645 00:35:16,982 --> 00:35:18,950 {\an8}The air that slammed into the ground 646 00:35:18,951 --> 00:35:22,453 {\an8}is now spreading out across the plains in a cold pool, 647 00:35:22,454 --> 00:35:24,156 {\an8}coming toward them. 648 00:35:25,357 --> 00:35:27,959 {\an8}Their radar tracks the dust kicked up 649 00:35:27,960 --> 00:35:32,064 {\an8}by the advancing bank of fast-moving cold air. 650 00:35:33,365 --> 00:35:34,799 So we're expecting 651 00:35:34,800 --> 00:35:36,501 that cold pool to come through 652 00:35:36,502 --> 00:35:37,869 within the next few minutes, 653 00:35:37,870 --> 00:35:39,270 so we're waiting to try 654 00:35:39,271 --> 00:35:40,772 to collect the data. 655 00:35:42,007 --> 00:35:45,409 The team will release weather balloons up into the cold pool, 656 00:35:45,410 --> 00:35:47,044 to measure temperature, pressure, 657 00:35:47,045 --> 00:35:49,381 humidity, and moisture. 658 00:36:04,796 --> 00:36:06,998 This cooling of the air you can feel, 659 00:36:06,999 --> 00:36:08,499 and the wind you're feeling, 660 00:36:08,500 --> 00:36:11,135 that's this boundary that's actually starting to hit us. 661 00:36:11,136 --> 00:36:13,304 So we're going to release that balloon. 662 00:36:13,305 --> 00:36:14,906 Everybody ready? 663 00:36:14,907 --> 00:36:17,910 Three, two, one. 664 00:36:22,481 --> 00:36:23,848 Oh, and there's some thunder. 665 00:36:23,849 --> 00:36:26,051 Please release. 666 00:36:37,362 --> 00:36:39,797 {\an8}30 minutes after the rain bomb dropped, 667 00:36:39,798 --> 00:36:41,866 {\an8}that bank of cold air, 668 00:36:41,867 --> 00:36:44,802 {\an8}here graphically rendered to be visible, 669 00:36:44,803 --> 00:36:48,406 {\an8}has covered the 17 miles from the epicenter of the storm 670 00:36:48,407 --> 00:36:52,210 {\an8}and breaks over the flying curtain of drones. 671 00:37:01,019 --> 00:37:05,389 On the ground, the team analyzes the data. 672 00:37:05,390 --> 00:37:08,459 So right here, we're, we're looking at data 673 00:37:08,460 --> 00:37:10,294 from the balloon that we just launched. 674 00:37:10,295 --> 00:37:12,496 What we're looking at is pressure, moisture, 675 00:37:12,497 --> 00:37:15,566 {\an8}temperature, and relative humidity. 676 00:37:15,567 --> 00:37:16,567 {\an8}And this is telling us 677 00:37:16,568 --> 00:37:18,002 {\an8}the depth of the cold pool 678 00:37:18,003 --> 00:37:19,470 {\an8}that just came through. 679 00:37:19,471 --> 00:37:21,172 {\an8}So right now, based on the temperature data, 680 00:37:21,173 --> 00:37:23,007 {\an8}we're seeing a decrease in temperature 681 00:37:23,008 --> 00:37:25,644 {\an8}that is going about 500 meters high. 682 00:37:27,112 --> 00:37:28,713 The team has learned the cold pool 683 00:37:28,714 --> 00:37:33,551 reaches 500 meters, or about 1,600 feet high, 684 00:37:33,552 --> 00:37:35,286 but that's not all. 685 00:37:35,287 --> 00:37:38,122 These balloon observations allow the team to measure 686 00:37:38,123 --> 00:37:42,460 what's happening to the air above the advancing cold pool. 687 00:37:42,461 --> 00:37:45,029 What they've found is that the cold pool 688 00:37:45,030 --> 00:37:50,234 acts as a wedge, pushing up an updraft of warm air. 689 00:37:50,235 --> 00:37:51,502 When we have a storm 690 00:37:51,503 --> 00:37:53,471 forming a really strong downburst 691 00:37:53,472 --> 00:37:55,373 and its associated cold pool, 692 00:37:55,374 --> 00:37:56,907 that lifts the surrounding air 693 00:37:56,908 --> 00:37:58,876 up and over the edge of the cold pool 694 00:37:58,877 --> 00:38:00,378 and forms a new updraft. 695 00:38:00,379 --> 00:38:03,881 That updraft can go on to build another really strong storm. 696 00:38:03,882 --> 00:38:07,118 That storm can then, of course, make its own downburst, 697 00:38:07,119 --> 00:38:08,552 its own new cold pool, 698 00:38:08,553 --> 00:38:10,287 which can then form another updraft, 699 00:38:10,288 --> 00:38:15,026 and so we get into this cyclical process of updraft formation. 700 00:38:17,562 --> 00:38:20,598 {\an8}Background winds can stretch downburst cold pools 701 00:38:20,599 --> 00:38:24,735 {\an8}from circular outflows into fan-shaped fronts. 702 00:38:24,736 --> 00:38:26,737 {\an8}If atmospheric conditions are primed 703 00:38:26,738 --> 00:38:28,806 {\an8}for multiple thunderstorms, 704 00:38:28,807 --> 00:38:31,876 {\an8}the cold pools can merge into one broad line 705 00:38:31,877 --> 00:38:34,378 {\an8}of advancing cold air. 706 00:38:34,379 --> 00:38:37,282 {\an8}The advancing boundary lifts warm air ahead of it. 707 00:38:38,417 --> 00:38:42,486 {\an8}This rising warm air feeds a new generation of updrafts 708 00:38:42,487 --> 00:38:45,690 {\an8}and helps build an even larger storm. 709 00:38:45,691 --> 00:38:47,558 {\an8}It's a self-sustaining cycle 710 00:38:47,559 --> 00:38:50,361 {\an8}of updrafts, downbursts, and cold pools 711 00:38:50,362 --> 00:38:53,031 {\an8}that sweeps across the landscape. 712 00:38:54,433 --> 00:38:58,203 {\an8}Meteorologists call this a derecho. 713 00:39:00,105 --> 00:39:02,406 {\an8}One thing that distinguishes derechos 714 00:39:02,407 --> 00:39:03,941 {\an8}from other types of wind systems 715 00:39:03,942 --> 00:39:06,877 {\an8}is their sheer size and how long they can last. 716 00:39:06,878 --> 00:39:10,981 {\an8}The longest one on record is some 1,300 miles. 717 00:39:10,982 --> 00:39:12,717 {\an8}Derechos can stick together 718 00:39:12,718 --> 00:39:15,486 {\an8}for time periods of six to 12 hours. 719 00:39:15,487 --> 00:39:19,490 {\an8}So these are extensive, very dangerous wind storms. 720 00:39:22,527 --> 00:39:26,997 {\an8}The 2024 Houston storm was a derecho-- 721 00:39:26,998 --> 00:39:30,901 {\an8}an organized system of multiple repeating downbursts 722 00:39:30,902 --> 00:39:34,438 {\an8}that ripped across a thousand miles of Gulf Coast 723 00:39:34,439 --> 00:39:38,477 {\an8}from Central Texas to the Florida Panhandle. 724 00:39:47,119 --> 00:39:49,854 {\an8}Back in Arizona, Mike has a hunch 725 00:39:49,855 --> 00:39:52,556 {\an8}that the beginnings of a multi-storm system 726 00:39:52,557 --> 00:39:55,327 {\an8}are brewing west along interstate eight. 727 00:39:56,495 --> 00:39:58,496 {\an8}Oh, man, this storm! 728 00:39:58,497 --> 00:40:00,931 {\an8}Big towers in the air going up. 729 00:40:00,932 --> 00:40:04,002 {\an8}Man, this is... This looks frigging great! 730 00:40:12,978 --> 00:40:15,246 {\an8}Oh, my God, look at this demon! 731 00:40:15,247 --> 00:40:18,649 {\an8}Holy rain bombs! 732 00:40:18,650 --> 00:40:20,018 {\an8}Now, that's a downburst! 733 00:40:21,386 --> 00:40:24,288 {\an8}We have a monster rain bomb right here, 734 00:40:24,289 --> 00:40:27,124 {\an8}a downburst of, like, that we haven't seen so far. 735 00:40:27,125 --> 00:40:29,661 {\an8}I mean, this looks like a bomb went off. 736 00:40:31,229 --> 00:40:33,864 {\an8}That thing just collapsed right on those mountains, 737 00:40:33,865 --> 00:40:36,467 {\an8}and all that air is just exploding and hitting us. 738 00:40:36,468 --> 00:40:39,603 This is awesome! 739 00:40:39,604 --> 00:40:41,272 I could see the towers up there. 740 00:40:41,273 --> 00:40:43,974 They were probably 50,000-plus. 741 00:40:43,975 --> 00:40:46,777 They were kind of twisting-- even right here, I see, like, 742 00:40:46,778 --> 00:40:48,712 this updraft has got a little twist to it, 743 00:40:48,713 --> 00:40:50,714 and when that happens, 744 00:40:50,715 --> 00:40:52,183 it's suspending that rain, 745 00:40:52,184 --> 00:40:53,784 because it's rotating, so it's suspending up there more, 746 00:40:53,785 --> 00:40:57,822 {\an8}so then, when it comes down, it just has so much more force. 747 00:40:57,823 --> 00:40:59,190 {\an8}And all that air, all the stuff we're feeling, 748 00:40:59,191 --> 00:41:02,226 {\an8}it's just blasting from that storm, 749 00:41:02,227 --> 00:41:05,930 {\an8}and it's constant, because there was probably multiple downbursts 750 00:41:05,931 --> 00:41:07,731 {\an8}that happened-- there was, like, an initial one. 751 00:41:07,732 --> 00:41:09,767 {\an8}There, there was one on the right, one on the left, 752 00:41:09,768 --> 00:41:11,769 {\an8}and then just, like, the main thing went down, 753 00:41:11,770 --> 00:41:14,605 {\an8}and now we're getting this dust that's appearing right here. 754 00:41:16,775 --> 00:41:20,845 {\an8}The dusty outflow winds from the rain bombs are racing west, 755 00:41:20,846 --> 00:41:23,314 and Mike jumps in his vehicle 756 00:41:23,315 --> 00:41:25,382 to get ahead of the growing storm 757 00:41:25,383 --> 00:41:27,651 and reset in a new position. 758 00:41:35,827 --> 00:41:37,828 {\an8}There's-- you can kind of make it out. 759 00:41:37,829 --> 00:41:40,098 So, we actually have a dust storm coming. 760 00:41:42,868 --> 00:41:45,904 So just overall, it's getting better as it goes west. 761 00:41:50,475 --> 00:41:52,409 Oof, lightning! 762 00:41:52,410 --> 00:41:54,479 {\an8}This dust in there is looking good. 763 00:41:56,548 --> 00:41:59,416 This dust is just food coloring in the atmosphere. 764 00:41:59,417 --> 00:42:03,587 {\an8}Basically, the dust and the shelf structure 765 00:42:03,588 --> 00:42:05,589 {\an8}are showing us the outflow, or the cold pool, 766 00:42:05,590 --> 00:42:06,924 {\an8}where it's all consolidated and pushing. 767 00:42:06,925 --> 00:42:08,359 {\an8}But without the dust, you don't get to see 768 00:42:08,360 --> 00:42:09,793 {\an8}what the air's actually doing. 769 00:42:09,794 --> 00:42:11,996 {\an8}This is gorgeous-- the color, this is what... 770 00:42:11,997 --> 00:42:12,997 {\an8}This is what you live for. 771 00:42:12,998 --> 00:42:15,299 {\an8}But this is the result 772 00:42:15,300 --> 00:42:17,234 {\an8}of stronger downbursts that consolidated 773 00:42:17,235 --> 00:42:19,638 {\an8}and just formed intense outflow. 774 00:42:22,674 --> 00:42:24,475 {\an8}This is amazing! 775 00:42:24,476 --> 00:42:26,378 {\an8}What?! 776 00:42:33,618 --> 00:42:35,654 {\an8}Whoa, it's making them disappear now! 777 00:42:44,729 --> 00:42:46,398 What a day! What a day! 778 00:42:54,773 --> 00:42:58,810 This dust storm produced winds of over 55 miles per hour. 779 00:42:59,945 --> 00:43:02,646 It was the result of multiple microbursts 780 00:43:02,647 --> 00:43:07,785 organizing into a larger system, creating a macroburst. 781 00:43:07,786 --> 00:43:10,721 {\an8}If this dust-filled cold pool had hit Phoenix 782 00:43:10,722 --> 00:43:12,489 {\an8}instead of the desert, 783 00:43:12,490 --> 00:43:15,492 {\an8}it could have caused extensive damage. 784 00:43:15,493 --> 00:43:20,664 {\an8}And if it had grown further, it could have become a derecho-- 785 00:43:20,665 --> 00:43:23,801 {\an8}exactly what hit Houston. 786 00:43:23,802 --> 00:43:28,339 {\an8}Downbursts and derechos are dangerous 787 00:43:28,340 --> 00:43:29,773 {\an8}wherever they strike, 788 00:43:29,774 --> 00:43:32,243 {\an8}but especially so when they hit built-up areas. 789 00:43:33,278 --> 00:43:36,481 {\an8}So is there any way to protect against them? 790 00:43:47,826 --> 00:43:50,427 Ian Giammanco is lead meteorologist 791 00:43:50,428 --> 00:43:54,031 at the Insurance Institute for Business and Home Safety, 792 00:43:54,032 --> 00:43:55,299 the IBHS. 793 00:43:55,300 --> 00:43:56,834 His team investigates 794 00:43:56,835 --> 00:44:00,337 how a downburst's devastating combination of wind and hail 795 00:44:00,338 --> 00:44:02,707 inflicts damage on property. 796 00:44:04,009 --> 00:44:05,776 {\an8}When wind attacks a building, 797 00:44:05,777 --> 00:44:08,412 {\an8}it's always looking for the weakest link in that chain. 798 00:44:08,413 --> 00:44:11,415 {\an8}And a lot of times, that is at the edges of roofs 799 00:44:11,416 --> 00:44:12,649 or if an opening, 800 00:44:12,650 --> 00:44:15,619 say, a garage door, a window, a door fails, 801 00:44:15,620 --> 00:44:17,187 and that air is allowed to rush in. 802 00:44:21,159 --> 00:44:22,960 They use a monster wind tunnel 803 00:44:22,961 --> 00:44:24,762 to test the construction standards 804 00:44:24,763 --> 00:44:27,998 of North American homes: 805 00:44:27,999 --> 00:44:31,403 an extraordinary array of 105 fans. 806 00:44:32,437 --> 00:44:35,305 Each fan is almost six feet in diameter 807 00:44:35,306 --> 00:44:37,809 and packs 350 horsepower. 808 00:44:39,711 --> 00:44:44,615 {\an8}Together, they can produce winds topping 100 miles per hour, 809 00:44:44,616 --> 00:44:47,384 {\an8}just like the Houston derecho. 810 00:44:50,321 --> 00:44:52,222 Wind is a cascade of damage. 811 00:44:52,223 --> 00:44:55,893 It often starts with one little thing 812 00:44:55,894 --> 00:44:59,329 that cascades to the next, to the next, to the next. 813 00:44:59,330 --> 00:45:00,531 And the next thing you know, 814 00:45:00,532 --> 00:45:02,600 you're looking at a catastrophic failure. 815 00:45:06,938 --> 00:45:09,506 To reinforce homes against the destructive power 816 00:45:09,507 --> 00:45:11,442 of downburst winds, 817 00:45:11,443 --> 00:45:13,744 Ian and the team at IBHS 818 00:45:13,745 --> 00:45:17,081 have developed a new building standard. 819 00:45:17,082 --> 00:45:18,348 It's designed to help 820 00:45:18,349 --> 00:45:20,150 minimize the amount of damage 821 00:45:20,151 --> 00:45:21,885 that comes with severe wind events. 822 00:45:25,323 --> 00:45:28,525 The IBHS construction methods include 823 00:45:28,526 --> 00:45:30,094 a hail-resistant roof, 824 00:45:30,095 --> 00:45:32,729 and also adds anchors and metal connectors 825 00:45:32,730 --> 00:45:34,164 to lock the roof to the walls 826 00:45:34,165 --> 00:45:37,134 and the walls to the foundations, 827 00:45:37,135 --> 00:45:40,805 transferring the wind's force down into the ground. 828 00:45:43,108 --> 00:45:45,109 Build a home to these standards 829 00:45:45,110 --> 00:45:47,344 and put it alongside a typical home, 830 00:45:47,345 --> 00:45:49,680 and the difference is clear. 831 00:45:55,320 --> 00:45:57,154 As our wind speeds increase, 832 00:45:57,155 --> 00:45:59,156 the front door fails. 833 00:45:59,157 --> 00:46:02,860 That allows wind to rush into that structure 834 00:46:02,861 --> 00:46:04,995 and start pushing out. 835 00:46:04,996 --> 00:46:07,731 The fortified home, however, sitting on its right, 836 00:46:07,732 --> 00:46:10,367 it's structurally sound-- it can take those forces, 837 00:46:10,368 --> 00:46:13,137 whereas the conventionally built home simply couldn't. 838 00:46:13,138 --> 00:46:17,074 And the next thing you know, the wall has failed... 839 00:46:18,243 --> 00:46:19,511 ...and it comes apart. 840 00:46:33,558 --> 00:46:35,192 As our atmosphere warms, 841 00:46:35,193 --> 00:46:37,728 that's simply producing more fuel for thunderstorms. 842 00:46:37,729 --> 00:46:39,396 It's air that wants to go up. 843 00:46:39,397 --> 00:46:41,198 Those thunderstorms can take advantage of that. 844 00:46:41,199 --> 00:46:42,766 {\an8}In a warming world, 845 00:46:42,767 --> 00:46:45,536 {\an8}you can store more water vapor in the air, 846 00:46:45,537 --> 00:46:48,472 {\an8}so as we have more of this fuel in the air 847 00:46:48,473 --> 00:46:50,174 {\an8}that can then condensate and release heat, 848 00:46:50,175 --> 00:46:52,776 {\an8}these thunderstorms, the derechos, 849 00:46:52,777 --> 00:46:54,746 {\an8}can become more intense. 850 00:46:55,780 --> 00:46:57,614 As the world warms, 851 00:46:57,615 --> 00:47:00,218 there will be more moisture in the atmosphere on average. 852 00:47:01,352 --> 00:47:04,721 But some regions could actually dry out. 853 00:47:04,722 --> 00:47:08,859 Drier air has to rise farther to cool enough to condense, 854 00:47:08,860 --> 00:47:11,495 so cloud bases would be higher. 855 00:47:11,496 --> 00:47:14,231 That could have big consequences. 856 00:47:14,232 --> 00:47:16,066 If you had a cloud base of this high 857 00:47:16,067 --> 00:47:18,135 and now you raise it to this high, 858 00:47:18,136 --> 00:47:20,771 you have so much dry air 859 00:47:20,772 --> 00:47:24,174 to put raindrops through, to put hailstones through, 860 00:47:24,175 --> 00:47:28,111 that it gives the storm system a lot more time 861 00:47:28,112 --> 00:47:30,147 {\an8}to evaporate and melt. 862 00:47:30,148 --> 00:47:32,449 {\an8}More evaporation and melting may mean 863 00:47:32,450 --> 00:47:35,052 {\an8}there is less precipitation hitting the ground, 864 00:47:35,053 --> 00:47:39,690 {\an8}but it also means faster-falling, cold, dense air. 865 00:47:39,691 --> 00:47:43,560 {\an8}And so there's every reason to expect, with changing climates, 866 00:47:43,561 --> 00:47:44,828 {\an8}stronger downbursts. 867 00:47:44,829 --> 00:47:47,998 {\an8}Derechos already became more powerful 868 00:47:47,999 --> 00:47:50,434 {\an8}over the last 40 years 869 00:47:50,435 --> 00:47:52,703 because the air is warmer over the U.S. nowadays 870 00:47:52,704 --> 00:47:54,438 than it was in the '80s. 871 00:47:54,439 --> 00:47:57,441 So, this is a race to get our building codes 872 00:47:57,442 --> 00:47:59,343 and get our structures ready to deal 873 00:47:59,344 --> 00:48:02,847 with what could be the weather of the future. 874 00:48:04,983 --> 00:48:07,884 Protecting homes and businesses will reduce 875 00:48:07,885 --> 00:48:11,321 the financial cost of future downbursts and derechos. 876 00:48:11,322 --> 00:48:15,425 And better forecasting is also essential. 877 00:48:15,426 --> 00:48:18,996 But weather forecasts face limits 878 00:48:18,997 --> 00:48:20,897 because of the inherently chaotic nature 879 00:48:20,898 --> 00:48:22,966 of the atmosphere. 880 00:48:22,967 --> 00:48:24,968 If you start a model 881 00:48:24,969 --> 00:48:27,838 with slightly different initial conditions, 882 00:48:27,839 --> 00:48:30,274 the end results can be very different 883 00:48:30,275 --> 00:48:32,909 based on some very simple differences 884 00:48:32,910 --> 00:48:36,480 in the initial information we put into our models. 885 00:48:36,481 --> 00:48:39,016 We can't actually accurately predict 886 00:48:39,017 --> 00:48:41,686 the weather beyond about 14 days. 887 00:48:42,687 --> 00:48:45,589 By updating the model every few minutes with live data, 888 00:48:45,590 --> 00:48:48,759 the forecast can be nudged back to reality. 889 00:48:48,760 --> 00:48:51,496 But data quality is crucial. 890 00:48:52,563 --> 00:48:56,801 And some of the best data comes from space-based instruments. 891 00:49:01,372 --> 00:49:03,408 {\an8}French Guiana. 892 00:49:10,748 --> 00:49:12,783 An Ariane 5 rocket delivers 893 00:49:12,784 --> 00:49:15,786 a 4.2-ton next-gen weather satellite 894 00:49:15,787 --> 00:49:18,455 into a geostationary orbit, 895 00:49:18,456 --> 00:49:22,193 where it stays positioned above Europe and North Africa. 896 00:49:23,294 --> 00:49:24,995 It's one of three satellites 897 00:49:24,996 --> 00:49:27,297 that will be co-located in the same orbit 898 00:49:27,298 --> 00:49:29,534 to probe the region's atmosphere. 899 00:49:31,669 --> 00:49:34,871 Olivier Brize is part of the team 900 00:49:34,872 --> 00:49:36,907 behind this new satellite system. 901 00:49:36,908 --> 00:49:40,744 The Meteosat mission is a geostationary satellite. 902 00:49:40,745 --> 00:49:45,283 {\an8}You have a constant and stable view of the Earth. 903 00:49:46,384 --> 00:49:49,986 The aim is to improve the short-term nowcasting 904 00:49:49,987 --> 00:49:53,690 and also to provide alerts on a severe weather event 905 00:49:53,691 --> 00:49:55,992 on a very short term, within one or two hours 906 00:49:55,993 --> 00:49:58,729 and within a very small area: 907 00:49:58,730 --> 00:50:01,332 on a valley, on a village, on a town. 908 00:50:05,703 --> 00:50:08,205 These satellites will provide a 3D profile 909 00:50:08,206 --> 00:50:11,141 of the atmosphere above Europe and North Africa, 910 00:50:11,142 --> 00:50:13,844 including humidity, 911 00:50:13,845 --> 00:50:16,012 wind speed, 912 00:50:16,013 --> 00:50:17,749 and temperature. 913 00:50:19,584 --> 00:50:22,719 This real-time view will enable forecasters 914 00:50:22,720 --> 00:50:25,288 to spot the warning signs of an atmosphere 915 00:50:25,289 --> 00:50:28,058 primed to produce downbursts: 916 00:50:28,059 --> 00:50:29,626 rapidly cooling cloud tops 917 00:50:29,627 --> 00:50:33,297 or banks of dry air around developing thunderstorms... 918 00:50:34,365 --> 00:50:37,769 ...allowing forecasters to give downburst warnings. 919 00:50:41,105 --> 00:50:43,707 For us working on this project, we are convinced 920 00:50:43,708 --> 00:50:46,844 that we are in a position to save lives. 921 00:50:47,945 --> 00:50:49,646 So far, the U.S. has 922 00:50:49,647 --> 00:50:52,616 no equivalent geostationary satellite system, 923 00:50:52,617 --> 00:50:55,420 but there are plans for future deployment. 924 00:50:56,454 --> 00:50:59,623 If we want to save lives around the world, 925 00:50:59,624 --> 00:51:03,894 we really need global observations, and so, 926 00:51:03,895 --> 00:51:07,197 the best way to do this is to build satellite platforms. 927 00:51:07,198 --> 00:51:09,933 We've made progress with the forecasting 928 00:51:09,934 --> 00:51:11,968 of extreme downbursts and derechos, 929 00:51:11,969 --> 00:51:13,670 but there's still a lot of things 930 00:51:13,671 --> 00:51:15,172 that we don't know about them. 931 00:51:15,173 --> 00:51:19,409 However, our modeling systems, our observational systems, 932 00:51:19,410 --> 00:51:20,944 and our field campaigns 933 00:51:20,945 --> 00:51:23,580 have allowed us to really move forward 934 00:51:23,581 --> 00:51:26,551 with understanding these storms and better predicting them. 935 00:51:27,618 --> 00:51:29,453 Earth's atmosphere is a cauldron 936 00:51:29,454 --> 00:51:32,923 mixing warm, wet air with cold air above, 937 00:51:32,924 --> 00:51:37,060 {\an8}a mixture that generates huge thunderstorms. 938 00:51:37,061 --> 00:51:39,596 And as the Earth's atmosphere warms, 939 00:51:39,597 --> 00:51:43,300 it will hold more moisture and more energy to fuel them. 940 00:51:43,301 --> 00:51:47,037 As we move forward with new satellite technology, 941 00:51:47,038 --> 00:51:49,506 I believe that our ability to forecast these systems 942 00:51:49,507 --> 00:51:52,610 will be even more improved in the next zero to ten years. 943 00:51:53,644 --> 00:51:56,713 But while we wait for forecasts to catch up, 944 00:51:56,714 --> 00:51:58,615 more severe winds, 945 00:51:58,616 --> 00:52:00,817 more deadly hail, 946 00:52:00,818 --> 00:52:03,520 and more extreme rainfall 947 00:52:03,521 --> 00:52:06,890 {\an8}will mean more devastating rain bombs.