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  • Tornadoes occur in every continent, except Antarctica

  • but more form over the central United States than anywhere else

  • in a zone called Tornado Alley.

  • That's because conditions in the Alley are ideal

  • for creating tornadoes.

  • Warm humid air low to the ground moves north

  • from the Gulf of Mexico

  • and collides with cool dry air high above the ground

  • rolling in from the Rocky Mountains.

  • The collision of air masses creates a supercell,

  • a massive thunderstorm that has a strong rotating updraft of air.

  • Scientists aren't exactly sure what happens next

  • but the leading idea goes like this:

  • The difference in speed between the faster high winds

  • and the slower low winds

  • causes the air in between to rotate around the horizontal axis.

  • If one end of the rolling air gets caught on the updraft

  • is bent upward and forms a funnel cloud.

  • Its spin gets tighter and faster

  • and the cloud gets longer.

  • Rain or hail from the thunderstorm

  • can then push down on the tail of the funnel cloud

  • until it reaches the ground, forming a tornado.

  • The top wind speed of most tornadoes

  • is usually under a 110 miles an hour,

  • and most touch the ground for less than ten minutes.

  • However, extreme tornadoes are truly extreme.

  • The longest tornado path was cut by the Tri-State tornado on March 18, 1925.

  • It tore up property for 219 miles

  • It was on the ground for well over three hours

  • and killed 747 people.

  • Which is why I'll be hanging out in here,

  • in Antarctica with the Penguins

  • until tornado season is over.

  • For Scientific American, Instant Egghead. I'm Mark Fischetti.

Tornadoes occur in every continent, except Antarctica

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竜巻はどのように形成されるのか?- インスタントエッグヘッド #37 (How Do Tornadoes Form? - Instant Egghead #37)

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    rcnwxiqtnqj に公開 2021 年 01 月 14 日
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