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They call me the tornado chaser.
大家都叫我“追风少年”。
When the wind is up and conditions are right, I get in my car and follow violent storms.
当起风和其他条件成立时，我就会跳上车，跟着那些龙卷风跑。
'Crazy,' you say? Perhaps, but really I chase these sky beasts to learn about them.
觉得我疯了吗？也许吧！但我只是想多了解它们一点。
I want to share with you what I know.
我想分享一下我的发现。
Tornadoes are rapidly rotating columns of air that form inside storms that connect with the ground via a funnel of cloud.
龙卷风是高速回旋的空气柱，在暴风中以漏斗状的云自天空延伸到地面。
When that happens, they tear across the Earth, posing a huge threat to life and property.
它们会横扫经过的地方，造成生命财产的重大损伤。
Because of this, there's a great deal of research into these phenomena,
为此有很多针对这个天然灾害的研究，
but the truth is, there's still a lot we don't know about how tornadoes form.
但对它形成的原因仍有许多未解之谜。
The conditions that may give rise to one tornado won't necessarily cause another.
一个龙卷风成形的条件，未必能让另一个龙卷风也成形。
But we have learned a lot since people first started recording tornadoes,
但自从人类第一次开始记录龙卷风，我们就已经了解了很多，
like how to recognize the signs when one is brewing in the sky.
比如说怎么辨认龙卷风在空中酝酿的征兆。
Are you coming along for the ride?
想知道是什么吗？
Tornadoes begin with a thunderstorm but not just any thunderstorm.
龙卷风的前兆是雷雨，但不是每次雷雨后都有龙卷风。
These are especially powerful, towering thunderstorms called supercells.
要充满能量、巨大的“超级雷雨胞”。
Reaching up to over 50,000 feet, they bring high force winds, giant hailstones,
高五万英尺以上，会带来强风、大冰雹，
sometimes flooding and great flashes of lightning, too.
有时甚至会是洪水、大闪电等。
These are the kinds of storms that breed tornadoes,
这就是孕育龙卷风的基本需求，
but only if there are also very specific conditions in place,
但还要再满足一些特定条件，
clues that we can measure and look out for when we're trying to forecast a storm.
那些我们可以测量、察觉到帮助我们预测龙卷风的指标。
Rising air is the first ingredient needed for a tornado to develop.
“上升气流”是首要条件。
Any storm is formed when condensation occurs, the byproducts of the clouds.
任何风暴形成前，水气都会先凝结，这是制造云的过程之一。
Condensation releases heat, and heat becomes the energy that drives huge upward drafts of air.
凝结时会放出热量，热量会变成推动庞大上升气流的能量。
The more condensation and the bigger the storm clouds grow, the more powerful those updrafts become.
水气凝结越多，就会制造越大的积雨云；又会推动更多上升气流。
In supercells, this rising airmass is particularly strong.
在超级雷雨胞中，这些的空气变得特别有力。
As the air climbs, it can change direction and start to move more quickly.
空气上升后可能会改变方向，开始快速移动。
Finally, at the storm's base, if there is a lot of moisture, a huge cloud base develops,
最后在云的底部，如果水气够的话，会发展成巨大的“云底”，
giving the tornado something to feed off later, if it gets that far.
如果龙卷风形成，就能所需提供能量。
When all these things are in place, a vortex can develop enclosed by the storm,
当一切就绪，云团中心会形成涡流，
and forming a wide, tall tube of spinning air that then gets pulled upwards. We call this a mesocyclone.
再发展成向上吸引的巨大管状旋风。我们称之为“中气旋”。
Outside, cool, dry, sinking air starts to wrap around the back of this mesocyclone,
外面的干冷下沉空气，开始从中气旋的后方卷入，
forming what's known as a rear flank downdraft.
形成所谓的“后侧下沉气流”。
This unusual scenario creates a stark temperature difference between the air inside the mesocyclone, and the air outside,
这样的现象会造成中气旋里外强烈的温差，
building up a level of instability that allows a tornado to thrive.
而这种不稳定会进一步助长龙卷风壮大。
Then, the mesocyclone's lower part becomes tighter, increasing the speed of the wind.
之后中气旋底部会收紧，风速因此增加。
If, and that's a big if, this funnel of air moves down into that large, moist cloud base at the bottom of the parent storm,
如果，我是说假如，这个漏斗状的气旋往下移，接触到雷雨胞下层潮湿丰沛的云底，
it sucks it in and turns it into a rotating wall of cloud, forming a link between the storm that created it and the Earth.
就会吸收云底变成快速旋转的云墙，最后再向下触及地面。
The second that tube of spinning cloud touches the ground, it becomes a tornado.
一旦这道快速旋转的云柱碰触到地面，就成了“龙卷风”。
Most are small and short-lived, producing winds of 65-110 miles per hour,
龙卷风大多小又短命，风速约每小时65到110英里，
but others can last for over an hour, producing 200 mile per hour winds.
但有些风速可达每小时200英里，而且维持一个小时左右。
They are beautiful but terrifying, especially if you or your town is in its path.
虽然很美但很恐怖，尤其是当你本人或你家在它的行进路线时。
In that case, no one, not even tornado chasers like me, enjoy watching thing unfold.
这时候，没有人，包括我这样的观察家在内，会想看接下来的后果。
Just like everything, however, tornadoes do come to an end.
就跟万物一样，龙卷风也有消失的时候。
When the temperature difference disappears and conditions grow more stable,
当温差消失、各项条件趋于稳定，
or the moisture in the air dries up, the once fierce parent storm loses momentum and draws its tornado back inside.
或是空气中的湿度降低，雷雨胞能量耗尽，龙卷风就会慢慢消散。
Even so, meteorologists and storm chasers like me will remain on the lookout, watching,
尽管到了这个阶段，气象学家或像我一样的追风少年，还是会继续盯着它，
always watching to see if the storm releases its long rope again.
看它会不会死灰复燃。
