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A ship in a force 12 ("hurricane-force") storm at sea, the highest rated on the Beaufort scale. The Beaufort scale (/ ˈ b oʊ f ər t / BOH-fərt) is an empirical measure that relates wind speed to observed conditions at sea or on land. Its full name is the Beaufort wind force scale.
The National Weather Service issues a similar high wind warning (Specific Area Message Encoding code: HWW) for high winds on land. The criteria vary from place to place; however, in most cases, the warning applies to winds of 40 miles per hour (64 km/h) to 73 miles per hour (117 km/h) for at least 1 hour; or any gusts of 58 miles per hour (93 km/h) to 114 miles per hour (183 km/h) on land.
This is followed by gale warnings (winds of force 8 or more on the Beaufort scale), if any (e.g., "There are warnings of gales in Rockall, Malin, Hebrides, Bailey, and Fair Isle"). This sometimes follows the opposite format (e.g., "There are warnings of gales in all areas except Biscay, Trafalgar and FitzRoy").
A gale is a strong wind; the word is typically used as a descriptor in nautical contexts. The U.S. National Weather Service defines a gale as sustained surface wind moving at a speed between 34 and 47 knots (63.0 and 87.0 km/h; 17.5 and 24.2 m/s; 39.1 and 54.1 mph). [1]
Storm scale or storm-scale may refer to: Intensity rating schemes for various types of storms: Antarctica Weather Danger Classification; Beaufort scale for storms at sea; Geomagnetic storm § Measuring intensity; Tornado intensity scales; Tropical cyclone intensity scales; Weather phenomena at meso-gamma scale, about the size of an individual ...
A diagram illustrating the relationship between the Beaufort, Fujita, and Mach number scales. The original scale as derived by Fujita was a theoretical 13-level scale (F0–F12) designed to smoothly connect the Beaufort scale and the Mach number scale. F1 corresponds to the twelfth level of the Beaufort scale, and F12 corresponds to Mach number ...
At some point, the lower limit was reduced to 23 miles per hour (20 knots). Today, however, most places have standardized on 25 to 38 miles per hour (22 to 33 knots), encompassing the combined ranges of forces 6 and 7 on the Beaufort scale. Winds strong enough to trigger a small craft advisory may be referred to as being advisory-force.
The scale was tested from 1972 to 1975 and was made public at a meeting of the Royal Meteorological Society in 1975. The scale sets T0 as the equivalent of 8 on the Beaufort scale and is related to the Beaufort scale (B), up to 12 on the Beaufort scale, by the formula: B = 2 (T + 4) and conversely: T = B/2 - 4