Q. Why do winds travel clockwise around high-pressure centers and counterclockwise around low-pressure centers? Is it different in the Southern Hemisphere?
A. Wind travels from areas of high pressure to areas of low pressure. Thus, the direction of the surface wind in a high-pressure weather system is basically outward, away from the system toward lower pressure. The wind’s direction in a low-pressure system is inward.
In the Northern Hemisphere, the turning of the earth on its axis results in deflection of the wind to the right. This is called the Coriolis effect, after Gustave-Gaspard Coriolis, the French scientist who first described it in 1835.
If the wind is moving inward, its deflection to the right results in a counterclockwise motion. If the wind’s motion is outward, the result is a clockwise spiral.
The effect is the opposite below the Equator, in the Southern Hemisphere. But meteorological authorities emphasize that this effect is only reliably seen in large-scale air masses. Small whirlwinds can spin in either direction, just as water spiraling down a drain can go in either direction, no matter which hemisphere the observer is in.