Naturalist's Almanac

Sir Francis Beaufort, who spent much of his life sailing tall ships and charting distant bodies of water for the British Navy, was born on May 7, 1774. He’s not famous enough that anyone celebrates his birthday, but he’s worth remembering at this time of year for his close observations of the wind.

He entered the navy at age thirteen and by 1805 had risen to the rank of captain. When he became responsible for his own ship’s log, it occurred to him that a uniform reference system for classifying different winds would offer more concise and useful log entries. So he began to observe his ship’s behavior.

Beaufort distinguished thirteen different levels of wind based on how his ship with its many sails responded. Zero meant too calm to sail. One through eleven meant winds from just strong enough to sail to winds almost too strong to bear. Twelve meant a wind “no canvas could withstand.”

In Beaufort’s day there were no instruments for measuring wind speed. So his observation-based system offered sailors the best way to at least rank the winds they encountered. It was so clear and simple that in 1838 the British Navy required all ships to use it in their logs.

Then, in 1846, came the first anemometer — an instrument that could measure exact wind speeds. It didn’t take long for wind watchers to see that if the speeds of Beaufort’s observed winds could be quantified with an anemometer, his scale could be used as a shorthand for wind speeds.

But there were several problems. Not everyone knew sailing ships as well as Beaufort did, so there was a need for new descriptions based on surface features of the sea. Then, of course, there was a need for descriptions that would work on dry land.

Furthermore, because the Beaufort scale was observation-based, its numbers depended on human judgments, making exact wind speed equivalents difficult to quantify. It took until 1926 to get a uniform set of equivalents accepted.

With the high-tech wind instruments available today, the Beaufort scale doesn’t get used much anymore. But it still works. Even a child who can describe what’s happening to wood smoke and trees can use Mr. Beaufort’s scale to estimate the speed of a local wind.

MORE INFORMATION

NOAA Storm Prediction Center
http://www.spc.noaa.gov/faq/tornado/beaufort.html

The Storm Prediction Center offers a reference chart that includes descriptions of the observable effects of Beaufort’s different winds both at sea and on land.

Stormfax Weather Almanac
http://www.stormfax.com/beaufort.htm

The Stormfax Weather Almanac offers a simplified master chart that includes the Beaufort number, the wind speed in both knots and mph, the wave height in feet, the World Meteorological Organizations’s description, the effects observed on the sea and the effects observed on land.

The Weather Doctor
http://www.islandnet.com/~see/weather/history/beaufort.htm

Keith C. Heidorn, a Canadian meteorologist who calls himself the Weather Doctor, has written a substantial history of Beaufort’s contributions to weather observation and record keeping. He puts the Beaufort Wind Scale in historic context, including an illustration of a British frigate, the vessel Beaufort used to describe the effects of different winds on a ship’s sails.