Beaufort scale
The Beaufort scale is an empirical measure for the intensity of the wind based mainly on sea-state or wave conditions. Its full name is the Beaufort wind force scale. It should be noted that the wave heights given pertain to the conditions found at open sea. The scale was created by the Irish naval commander Sir Francis Beaufort around 1805.
The initial scale did not have wind speeds, but listed a set of qualitative conditions from 0 to 12 by how a naval vessel would act under them - from 'just sufficient to give steerage' to 'that which no canvas could withstand'.
The scale was made a standard part of log entries for Royal Navy vessels in the late 1830s. The scale was adapted to non-naval use from the 1850s, with the Beaufort numbers being tied to cup anemometer rotations.
The rotations to number was standardised only in 1923 and the measure was slightly altered some decades later to improve its utility for meteorologists. Today, hurricanes are sometimes numbered 12 through 16 using the Saffir-Simpson Hurricane Scale, with a Category 1 hurricane bearing Beaufort number 12, a Category 2 hurricane, Beaufort 13, and so on. In the United States, winds of Beaufort 6 or 7 result in the issuance of a small craft advisory, with force 8 or 9 winds bringing about a gale warning, 10 or 11 a storm warning (or "tropical storm warning"), and anything stronger a hurricane warning.
External linksUK Meteorological Office history page on Beaufort ScaleUK Meteorological Office description page on Beaufort ScaleInvestigating Clouds : A lesson plan from the National Science Digital Library that uses the Beaufort Scale.US National Weather Service description of Beaufort Scale : Includes photos of accompanying sea appearance.
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