Original film · Weather
Why do hurricanes spin? The Coriolis effect, explained
Air rushing into a low turns right north of the equator and left south of it, so storms spin opposite ways. At the equator the effect vanishes, and so do hurricanes. Not your sink, though.
Transcript
Why do hurricanes spin? It starts with low pressure. Warm, rising air over the ocean leaves a low at the surface, and air rushes in from every side to fill it. If Earth stood still, that air would flow straight to the middle. But Earth turns. Ground at the equator moves east at nearly seventeen hundred kilometers an hour, while ground near the poles barely moves. So north of the equator, air heading north carries extra eastward speed, and drifts right. Air heading south drifts right too. That drift is the Coriolis effect. In the north, every inflowing stream curves the same way, and the whole storm turns counterclockwise. Now drag the storm across the equator. In the south, the drift flips to the left, and storms spin clockwise. Now bring the storm to the equator itself. The Coriolis effect drops to zero. Nothing turns the inflow, so hurricanes almost never form within about five degrees of it. And no: it's far too weak to decide which way your sink drains. Try it yourself at Explainer Tools dot com.