Beaufort scale


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Beaufort scale,

a scale of windwind,
flow of air relative to the earth's surface. A wind is named according to the point of the compass from which it blows, e.g., a wind blowing from the north is a north wind.
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 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 scaleFujita scale
or F-Scale,
scale for rating the severity of tornadoes as a measure of the damage they cause, devised in 1951 by the Japanese-American meteorologist Tetsuya (Ted) Fujita (1920–98).
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 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 scaleSaffir-Simpson scale
, standard scale for rating the severity of hurricanes as a measure of the damage they cause; it is based on observations of numerous North Atlantic Basin hurricanes.
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 for hurricanes was formulated by Herbert Saffir and Robert Simpson.

Bibliography

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

Beaufort Scale

 

a conventional scale for the visual estimation of the force (speed) of the wind, expressed in numbers, by its action on surface objects or wave agitation on the surface of the sea. It was devised by the English admiral F. Beaufort in 1806; at first it was used only by Beaufort himself. In 1874 it was accepted by the Permanent Committee of the First Meteorological Congress for general international

Table 1. Wind force at the earth’s surface according to the Beaufort scale (at a standard altitude of 10 m above an open, even surface)
Beaufort no.Descriptive term tor wind torceWind speed (m/sec)Action of wind
on landon the surface of the sea
0Calm0–0.2Calm. Smoke rises vertically.Smooth, calm.
1Quiet0.3–1.5Direction of wind shown by smoke drift but not by wind vanes.Ripples, no spray on the crests.
2Light breeze1.6–3.3Wind felt on face, leaves rustle, wind vane moved by wind.Short waves. The crests do not break and are glassy.
3Gentle breeze3.4–5.4Leaves and small twigs in constant motion, wind extends light flag.Short, well defined waves. Crests break, form glassy spray; occasionally whitecaps form.
4Moderate breeze5.5–7.9Wind raises dust and paper, moves small b-anches.Long waves, whitecaps are frequent.
5Fresh breeze8.0–10.7Small trees sway, small waves crest on water.Long, but not very large waves, whitecaps are everywhere (spray sometimes forms).
6Strong breeze10.8–13.8Large branches in constant motion, wires on telephone poles hurr.Large waves form. Large number of foamy crests (spray is likely).
7Moderate gale13.9–17.1Large trees sway, walking against wind difficult.Waves become large, crests break, foam forms in band on the windward side.
8Fresh gale17.2–20.7Twigs break off trees, walking against the wind very difficult.Moderately high, long waves. Spray is blown from the crests. Bands of foam lie in strips in the direction of the wind.
9Strong gale20.8–24.4Minor damage; the wind blows off chimneys and tile.High waves. Foam lies on the windward side in wide, solid bands. Wave crests begin to break and form spray which decreases visibility.
10Whole gale24.5–28.4Considerable damage to buildings, trees are uprooted. Rare on dry land.Very high waves with long crests which are bent down. Foam is blown by the wind in large clumps of thick, white stripes. The surface of the sea is white with foam. The noise of the waves sounds like blows. Visibility is poor.
11Storm28.5–32.6Widespread damage. Seldom observed on dry land.Extremely high waves. Small and medium size vessels disappear from view from time to time. The sea is covered by long, white flecks of foam, collecting on the windward side. The edges of waves are covered with foam. Visibility is poor.
12Hurricane32.7 and higherWidespread damage. Seldom observed on dry land.The air is filled with foam and spray. The sea is covered with bands of foam. Very poor visibility.

synoptic usage. In subsequent years the Beaufort scale was changed and improved. In 1963, the International Meteorological Organization accepted the Beaufort scale given in Table 1 for general practice. The Beaufort scale is widely used in navigation.

K. P. VASIL’EV

Beaufort scale

A set of descriptive terms of wind strength, evolved according to the effect of wind upon sailing craft and sea disturbance. Captain Beaufort devised the scale in 1806. The scale is depicted in the illustration. (See page 102)

Beaufort scale

Meteorol an international scale of wind velocities ranging for practical purposes from 0 (calm) to 12 (hurricane force). In the US an extension of the scale, from 13 to 17 for winds over 64 knots, is used
References in periodicals archive ?
A revised Beaufort scale was then used as an official system for measure.
The Met Office said the highest recorded gust of wind in the region was 48mph - classed as a severe gale on the Beaufort Scale - at around 3pm in Church Lawford, between Coventry and Rugby.
A powerful Atlantic weather front span across the South overnight, packing winds ranked force 11 of 12 on the Beaufort Scale.
In the same column we said Sir Francis Beaufort invented the Beaumont scale - it should, of course, have said the Beaufort scale.
Reading it in conditions exceeding 0 on the Beaufort Scale was akin to wrestling a giant butterfly.
A biting wind blew directly down the pitch to play a crucial part in proceedings, although given that Chicago finishes a distant second to Billesley Common on the Beaufort Scale, perhaps Moseley should have adapted better than they did.
A Holyhead Coastguard spokeswoman said: ``Mainly the winds were gusting at 9-10 on the Beaufort scale, gale force winds.
The result is that in our classrooms young children who still need to establish essential foundation skills in reading, writing and number have spent hours on topics like photosynthesis and the Beaufort scale of wind strength - subjects that their own teachers did not study until secondary school
Strong winds, reaching gusts of seven on the Beaufort scale are also expected, especially on Tuesday and Wednesday, mainly in the coastal areas.
What is the highest number on the Beaufort Scale (representing a hurricane)?
He said: "On the way down, the waves were so large they reached around 40 to 50 feet and were completely off the Beaufort Scale.
Ophelia packs 96kmh winds classed as "violent storm-force," touching category 11 of 12 on the Beaufort Scale, covering a huge area around 650km wide.

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