What caused Wednesday’s wind?

Ellen Bacca uses a balloon to demonstrate a high pressure area. (March 9, 2017)


GRAND RAPIDS, Mich. (WOOD) — Strong bursts of wind are expected with thunderstorms, but Wednesday’s wind raked across Michigan under mostly sunny skies. The reason behind the high winds is, of course, science.

Air always travels from high to low pressure, and there was a huge pressure difference nearby on Wednesday.

A good way to visualize how air moves through our atmosphere is to think of a balloon. Air inside the balloon is under relatively higher pressure than the air outside the balloon. That’s why, if given the chance, air will escape through any holes in the balloon, flowing from high pressure to lower pressure.

The air in the atmosphere follows this same law. It flows from high pressure to low pressure.

However, because Earth is constantly spinning, air traveling on our planet will swirl, too.  Air will travel around and away from a high pressure area. That air will rush away from areas of high pressure, swirling counter-clockwise until it collides at the center. This collision of air shoots clouds and storms high into the sky around areas of high pressure.

Wednesday, West Michigan was caught in the space between high and low pressure. So even though the rain and snow weren’t even close to our state, we saw the rush of wind.

Here is how it looked from space. The swirl north of Michigan is the center of low pressure, where the air was colliding.

Pressure differences are caused by unequal heating of the earth. This happens on a small scale, where different soils heat faster than others, for example. It also happens on much larger scales. In fact, in the subtropics, there is a permanent belt of high pressure because the Earth heats more at the equator than at the poles.

Wednesday’s storm was very strong, as far as low pressure systems go. Several wind gusts it generated were near 60 mph across West Michigan.

Peak wind gusts Wednesday March 8th via the National Weather Service

To put it into perspective, a thunderstorm producing wind is considered “severe” if it can produce wind gusts of more than 58 mph. Several wind reports Wednesday would have been in the “severe” category if a thunderstorm had produced them.

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