00:00Each year, damaging winds and tornadoes wreak havoc across the United States.
00:05The ingredients that produce them are nearly identical with one small difference.
00:12Wind shear.
00:14What is wind shear?
00:16Well, it's the changing wind direction or speed over a vertical or horizontal distance,
00:22and it is one of the main ingredients for severe weather.
00:26That's the difference between the two.
00:28Speed shear is increasing wind with height, but notice the direction stays the same.
00:36That's how you get straight line wind damage with severe thunderstorms.
00:40Now, tornadoes are a little different.
00:42You get what we call directional wind shear.
00:45What does that mean?
00:46That means the wind direction changes with height.
00:50It also increases in speed.
00:53And it's that changing wind direction with height that causes the air to spin and causes a horizontal circulation.
01:04Now, that circulation in the horizontal remains until what happens?
01:11You get a strong, what we call updraft.
01:15That's increasing motion from the surface through the upper part of the atmosphere.
01:21And what it does is it then stretches that horizontal circulation into the vertical,
01:27and that's how you get the tornado.
01:30A lot of ingredients that are the same, but the one difference is the wind shear.
01:36So, let's down to thehan inevitably in the rain near the ceiling,
01:36and that Adventure could leave the lavater either.
01:36And it's the wind shear.
01:37So, the Moon is the wind Heather.
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