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.

Related Topics:
Intensity - Wind - Wave - Sea

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The scale was created in 1806 by Sir Francis Beaufort, a British naval officer. 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.

Related Topics:
Francis Beaufort - 1830s

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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.

Related Topics:
1850s - Anemometer - 1923 - Saffir-Simpson Hurricane Scale

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The scale is used in, and may be most recognisable to some from, the Shipping Forecasts broadcast on BBC Radio 4 in the United Kingdom.

Related Topics:
Shipping Forecast - BBC Radio 4 - United Kingdom

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This scale is also widely use in China. Taiwan uses the Beaufort scale extended in 1944 with Forces 13-17 to better represent the wind caused by typhoons. Hong Kong and mainland China keep using Force 12 as the maximum. Macau adopted a set of simpler descriptions (calm, light, gentle, moderate, strong, gale, storm, hurricane) instead of the force numbers and descriptions in the table.

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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" for 8 to 11 if related to a tropical cyclone), and anything stronger a hurricane warning.

Related Topics:
United States - Small craft advisory - Gale warning - Storm warning - Tropical cyclone - Hurricane warning

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