(单词翻译:单击)
The average tornado has a lifespan of just a few minutes, but that's more than enough time for one of the world's most-destructive weather events to form.
龙卷风的平均寿命只有几分钟，但这是足以形成世界上最具破坏性的天气事件之一。
The most extreme tornadoes can last for hours, span miles in diameter, and whip up wind speeds over 300 miles per hour.
最极端的龙卷风可以持续数小时，直径达数英里，风速高于300英里每小时。
To prepare for these dangerous weather events, meteorologists have spent decades researching how tornadoes come to be.
为了应对这些危险的天气事件，气象学家花了几十年的时间研究龙卷风是如何形成的。
Tornadoes develop out of what's called a supercell thunderstorm, which is a normal thunderstorm with a persistent rotating updraft at its core.
龙卷风是由超级单体雷暴形成的，这是一种普通的雷暴，其核心是持续旋转的上升气流。
This rotating updraft grows into something called a vortex, a spinning column of air at the center of the storm.
这种旋转上升气流形成了所谓的漩涡，即风暴中心旋转的空气柱。
As a supercell grows in size, the vortex in the middle will begin to tilt, pulling warm air and moisture upward and pushing cold dry air down toward the ground.
随着超级单体规模的增大，中间的漩涡将开始倾斜，将暖空气和湿气向上拉，将寒冷干燥的空气推向地面。
The updraft of warm air causes the vortex to swell with water vapor, creating a spiraling funnel cloud.
暖空气上升气流导致涡旋与水蒸气膨胀，形成螺旋漏斗云。
The cool downdraft begins to battle the funnel cloud's upward spiral, focusing the cloud into a smaller area and increasing its speed.
冷空气开始与漏斗云的上升螺旋作战，使漏斗云聚集在越来越小的区域，并增加其速度。
With enough pressure and weight from the battling hot and cool air, the funnel cloud is forced down to the ground, and a tornado is born.
有了来自冷热空气的足够的压力和重量，漏斗云被迫降落到地面，龙卷风就诞生了。
Modern technologies like Doppler radar allow meteorologists to track the moisture and pressure in the air,
多普勒雷达等现代技术帮助气象学家追踪空气中的湿度和压力，
allowing them to notice the early stages of a tornado forming before the funnel cloud is even visible,
这让他们能够在可见漏斗云出现之前就注意到龙卷风形成的早期阶段，
and with every second of early warning, more damage can be prevented and more lives saved.
每早一秒的预警，就可以避免更多的损失，挽救更多的生命。
