An Overview of Buys Ballot's Law

If you study weather, it’s probable that you’ve heard of Buys Ballot’s Law.

In meteorology, Buys Ballot's law states that, in the Northern Hemisphere, if a person stands with his back to the wind, the atmospheric pressure is low to the left and high to the right.

This is because wind travels counterclockwise around low-pressure zones in the Northern Hemisphere. In higher latitudes of the Northern Hemisphere, this is approximately true. In the Southern Hemisphere, it is reversed.  

However, the angle between the pressure gradient force and the wind is not a right angle in low latitudes. If you turn your back to the wind, at lower latitudes in the northern hemisphere, the low-pressure centre will be to your left and somewhat toward the front.

First deduced from Ferrel’s Law by William Ferrel and J.H. Coffin, Buys Ballot’s Law takes the name of the man that first offered published empirical data. It is used by sailors to establish the location of low-pressure systems and their movement. When used in conjunction with a barometer, observation of clouds, wind speed and sea state Buys Ballot’s Law allows a sailor to best navigate a depression or severe storm by establishing the location, speed and direction of a low-pressure system and/or determining whether you are avoiding the dangerous quadrant of a tropical revolving storm or Hurricane.

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