Beaufort scale

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Beaufort scale, a scale of wind velocity devised (c.1805) by Admiral Sir Francis Beaufort of the British navy. An adaptation of Beaufort's scale is used by the U.S. National Weather Service; it employs a scale from 0 to 12, representing calm, light air, light breeze, gentle breeze, moderate breeze, fresh breeze, strong breeze, moderate gale, fresh gale, strong gale, whole gale, storm, hurricane. Zero (calm) is a wind velocity of less than 1 mi (1.6 km) per hr, and 12 (hurricane) represents a velocity of more than 74 mi (119 km) per hr.

Beaufort's original scale was later correlated to wind speed in two different ways. The U.S. and British scale is for winds measured at a 36-ft elevation, while the international scale requires only a 20-ft elevation. The Beaufort scale is the oldest method of judging wind force. Separate scales for tornadoes and hurricanes did not come until the 1970s. The Fujita scale for tornadoes was proposed in 1971 by Tetsuya (Ted) Fujita; in 2007 the Enhanced Fujita scale, incorporating improved knowledge of wind destruction, as was adopted. Soon after the development of the Fujita scale the Saffir-Simpson scale for hurricanes was formulated by Herbert Saffir and Robert Simpson.

See A. Shaw, Beaufort Wind Scale (1995).

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Beaufort scale Named after the 19th-century British naval officer who devised it, the Beaufort Scale assesses wind speed according to its effects. Originally designed in 1806 as an aid for sailors, it has since been adapted for use on land and was internationally recognised in 1874.

Scale

Wind speed

Name

km/h

mph

0

0–1

0–1

Calm

1

1–5

1–3

Light air

2

6–11

4–7

Light breeze

3

12–19

8–12

Gentle breeze

4

20–28

13–18

Moderate

5

29–38

19–24

Fresh

6

39–49

25–31

Strong

7

50–61

32–38

Near gale

8

62–74

39–46

Gale

9

75–88

47–54

Strong gale

10

89–102

55–63

Storm

11

103–117

64–72

Violent storm

12–17

118+

73+

Hurricane


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Beaufort scale Scale of values, from 0 to 12, for describing wind strength, as defined by Admiral Beaufort in the nineteenth century. Each wind force is recognized by its common effects on objects in the landscape (dust, flags, trees, etc.) and on people in the open, or on the state of the sea surface. See also SAFFIR/SIMPSON SCALE; and FUJITA TORNADO INTENSITY SCALE.

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Beaufort scale A scale of values, from 0 to 12, for describing wind strength, as defined by Admiral Sir Francis Beaufort (1774–1857) in 1806 (the scale was accepted by the British Admiralty in 1838 and adopted by the International Meteorological Committee in 1874). Each wind force is recognized by its common effects on objects in the landscape (dust, flags, trees, etc.) and on people in the open, or on the state of the sea surface.

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Beau·fort scale / ˈbōfərt/ a scale of wind speed based on a visual estimation of the wind's effects, ranging from force 0 (less than 1 knot or 1 kph, “calm”) to force 12 (64 knots or 118 kph and above, “hurricane”).