Atmosphere And Weather

The Beaufort Wind Scale

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The Beufort wind scale was devised in 1805 by Commander Francis Beufort (1774-1857), a young British navel officer who had just been given his first command, the HMS Woolwich. Wind scales were not new. The author Daniel Defoe, writing in 1703, referred to the use of wind scales, and records indicate they were being used at least as far back as the sixteenth century. In the early 1800s several scales were in sue, including one developed by the British Palantine Society (a precursor of the Royal Navy's Meteorological Office).

Beufort's original scale listed 13 stages of wind conditions ranging from ranging from "Faint air, just not calm" and "light airs" (1 and 2) to "Storm" (13). In 1807, he combined revised his scale by combining the first two categories, producing a 12-point scale. Interestingly enough from our modern point of view, there no specific wind speeds for the points on the scale. Rather, each point was a category that included a concise description of the weather conditions, including how the sea would look and how a fully-rigged sailing ship would behave. Perhaps most importantly, the scale told a sailor how much canvas (sail) a ship could carry without straining wooden masts and yardarms to the breaking point. For example, for wind conditions at 6 on the Beufort scale (Strong breeze) a ship could carry "single-reefs and top-gallants."

In 1812 Beufort was disabled in an encounter with Ottoman Turks off the coast of Asia Minor (now Turkey), and this might have been the end of his scale. He continued to serve in the Royal Navy, though restricted to shore duty, and became Hydrographer in the new Meteorological Office in 1829. In 1831 he commissioned what was to become one of the most famous scientific expeditions in history, the 5-year voyage of the HMS Beagle (best known for the theory of evolution later proposed by the expedition's naturalist, Charles Darwin). This was the first official use of Beufort's wind scale. Shortly thereafter (1832), it was finally published. In 1838, two years after the Beagle's safe return, the Royal Navy formally adopted the Beufort scale.

The Beaufort scale is not a static system; instead it has been revised from time to time, mainly to keep it current with the changing capabilities of ships brought about by technological advances. In 1903, specific wind speeds were added, using this formula: 1.87 times the square root of the cube of B (the Beufort number). For a strong breeze, this would be 1.87 times the square root of 6 cubed, or about 27 knots (about 31 miles per hour). In 1944, the Beufort scale was extended to 17 categories, including the conditions encountered in severe hurricanes, and again modified in 1960 to include information on likely wave heights.

The Beufort scale is still used today. However, in 1906 it was realized that steamships needed a different set of guidelines, and British meteorologist George Simpson developed an alternative which is also used. Simpson also produced a wind scale based on the old Palatine Society scale for use in evaluating wind conditions on land.

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