Buys Ballot's law

In meteorology, Buys Ballot's law (Dutch pronunciation: [ˈbœyz bɑˈlɔt]) may be expressed as follows: In the Northern Hemisphere, if a person stands with their back to the wind, the atmospheric pressure is low to the left, high to the right.

The information from many ships about individual voyages was compiled ashore and later became what today is still published by England, a 3 volume set complete with charts titled "Sailing Directions for the World".

However, the British Meteorological Office began to use Buys Ballot's law extensively after reintroducing a storm warning system in 1867 following the death of its former director Robert FitzRoy.

Included in the Sailing Directions for the World are Buys Ballot's techniques for avoiding the worst part of any rotating storm system at sea using only the locally observable phenomena of cloud formations, wind speed and barometric pressure tendencies over a number of hours.

The underlying principles of Buys Ballot's law state that for anyone ashore in the Northern Hemisphere and in the path of a hurricane, the most dangerous place to be is in the right front quadrant of the storm.

Although the principles apply to a very limited extent to a coastal observer during the approach and passage of a storm in any location, Buys Ballot's law was primarily formulated from empirical data to assist ships at sea.