How do tornadoes rip roofs off? © Getty Images

How do tornadoes rip roofs off?

It has nothing to do with the Wizard of Oz in case you were wondering.

Asked by: Bob Wilcox, Peterborough

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In the US, around one-third of tornadoes are strong enough to take the roofs off houses. They do this via a double-whammy effect: the fast-moving wind causes a sudden pressure drop over the roof, while debris trapped in the vortex smashes doors and windows, triggering an inrush of air that increases the pressure under the roof. The resulting pressure difference then rips the roof off.


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