Why do low-pressure systems turn anticlockwise? © Getty

Why do low-pressure systems turn anticlockwise?

You spin me right round baby, right round.

Asked by: Roger Evans, Argyll

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As the Earth spins, the speed of rotation experienced at the equator is much faster than at the North Pole. This difference causes the ‘Coriolis effect’ – a force which appears to deflect winds towards the right in the northern hemisphere.

© Peter Sucheski
© Peter Sucheski

In a low pressure weather system, air flows inward, but this deflection twists the air flow towards the right, creating an anticlockwise swirl of winds. In a high pressure system, air flows outward, and the deflection results in a clockwise rotation. The Coriolis effect deflects winds towards the left in the southern hemisphere, so weather systems here spin in the opposite direction.

Why can’t we feel atmospheric pressure? © Getty Images

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