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.
Robert is a science writer and visiting professor of science at Aston University.