Behind the Forecast: How the wind works

Listen to Science Behind the Forecast with Meteorologist Tawana Andrew every Friday on 89.3 WFPL at 7:45 a.m.
Updated: Jun. 12, 2020 at 9:11 AM EDT
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LOUISVILLE, Ky. (WAVE) - You’re eating outside at your favorite restaurant. It’s a beautiful sunny day, but your napkins keep flying off the table. You get tired of chasing little pieces of paper around the restaurant’s patio and shake your fist at the sky. Don’t fret; the wind won’t last forever.

The wind is simply air in motion in response to differences in atmospheric pressure. Those differences are caused by the planet's surface unevenly absorbing solar radiation. Due to this, wind speeds are typically highest during the day when those temperature and pressure differences are more pronounced.

In our atmosphere, wind moves more horizontally than it does vertically. Winds are defined by the compass direction of their origin. So wind from the west moving to the east is a westerly wind.

At the planet's surface, horizontally, wind moves from areas of high pressure to areas of low pressure. Vertically, the wind moves from low pressure to high pressure. The rate of air pressure change between the high and low-pressure centers usually determines the wind speed. The pressure change over a particular distance is called the pressure gradient force. The larger the pressure gradient force, the faster the winds.

The Earth's rotation creates another force, the Coriolis Force. The Coriolis force works against the pressure gradient force, changing the wind direction. In the Northern Hemisphere, the wind is deflected to the right of its original path. In the Southern Hemisphere, the wind is deflected to the left. The Coriolis Force's impact is more dramatic depending on the wind velocity and the latitude. Coriolis Force is greatest at the poles and is absent at the equator. It only affects the wind direction, not speed.

As a side note, the Coriolis Force does not affect your toilet.

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