Weather Whys: How are straight-line winds different from tornadoes?

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Straight-line wind damage is often mistaken for tornado damage by the average person, but these winds are very different from tornadoes. Here’s what can make it so confusing: 

  1. Straight-line winds have a similar debris pattern to tornadoes.
  2. They can cause a lot of damage, and even tip mobile homes. People may just assume it had to be a tornado.
  3. They both occur with strong thunderstorms.

There are several differences, though. If you didn’t witness the storm, you can still figure out if the damage was caused by a tornado or by straight-line winds. 

Tornadoes form due to rotation in a thunderstorm. This rotation will shape the debris pattern you find left behind by a tornado. They are also “smaller scale” events, meaning they do not typically impact a large area. Thanks to the rotation, you will find debris lying in several different directions after a tornado moves through.

Straight-line winds leave behind a different debris pattern. These winds, true to their name, follow a straight line. The debris field will too. If straight-line winds impact an area of trees, the trees will all fall in about the same direction. This can make identifying straight-line winds easier. They can also impact a much larger area.

Straight-line winds form as a result of the downdraft in a thunderstorm. As the air heads out of the storm and toward the ground, it speeds up, thanks in part to evaporative cooling. As moisture evaporates, the air cools. Cold air is more dense than warm air so it sinks faster and faster. By the time it hits the ground, it is moving at a very high speed. The downdraft makes contact with the surface and spreads out across the ground, then travels along the ground in a straight line and causes damage until the wind weakens.

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