How do tornadoes rip roofs off?

Asked by: Bob Wilcox, Peterborough

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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