Although the Coriolis effect doesn't determine the direction of toilet flushes or knuckle balls, it does have a significant impact on weather patterns. If you've ever watched The Weather Channel, you've probably noticed all those arrows swirling around the meteorologist's map to indicate wind direction. The direction those arrows are pointing toward is largely determined by the Coriolis effect.
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If the Earth didn't rotate, winds would travel either north or south due to differences in temperature and pressure at different latitudes. But since the Earth does rotate, the Coriolis force deflects these winds to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
In the Northern Hemisphere, this deflection causes the wind flow around high pressure systems to go clockwise while flow around low-pressure systems travels counterclockwise. Imagine a low-pressure system as a vacuum that sucks all the surrounding air straight towards it, creating many vectors of wind that all focus on one spot. Because of the Coriolis effect, each of these vectors gets twisted to the right, which in turn creates a counterclockwise flow. With a high-pressure system, air gets forced outward and the Earth's eastward spin creates a clockwise flow. In the Southern Hemisphere, the opposite takes place: Wind around low-pressure systems circles clockwise while wind around high-pressure systems circles counterclockwise.
The swirling motions around low-pressure systems are actually the driving forces behind hurricanes. The air gets sucked in with such force and spins to such a degree that a potentially destructive storm develops. Warm ocean water fuels the system and if it gets a chance to grow over a period of time, powerful winds of more than 62 miles per hour (100 kilometers per hour) can form a storm strong enough to destroy anything in its path -- all just from the spin of our little planet.
The curvature of the winds created by the Coriolis effect also helps create surface ocean currents. The wind drags on the water's surface, creating spiral currents called gyres. As you may have guessed, the gyres in the Northern Hemisphere spin clockwise and the ones in the Southern Hemisphere spin counterclockwise.
Meteorologists and sailors aren't the only ones who have to contend with the Coriolis effect. Since aircraft cover large distances in a short period of time, pilots must also take its influence into account when charting the paths for their flights. For instance, a plane headed from Miami (where the Earth's rotation is more pronounced) to New York would end up in the Atlantic Ocean if the pilot ignored the effects of the Earth's rotation.