Atmosphere And Weather
Beaufort Scale 12

The Beaufort Scale

Beaufort Scale 12
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"The Beaufort Scale"
Caption: Beaufort Scale 12
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© Public Domain in the US because it is a work by an employee of the US Govt as part of official duty

The Beaufort Wind Scale has for almost two hundred years been the standard method of observing and recording wind conditions in maritime and coastal environments. The thirteen point scale being used in many shipping forecasts to indicate the experienced and expected wind conditions.

The Beaufort is named for Sir Francis Beaufort, the man credited with devising the wind force scale. In the early 1800s, Commander Beaufort, as he was then, was captain of the fifth-rate frigate, HMS Woolwich. Part of the responsibilities of the captains of Royal Naval vessels was the recording of sea and weather conditions encountered, although there was no standard system to record the observations. Beaufort therefore came up with his own scale, based on observations of the ship’s sails and the sea condition around. This initial scale was said to have been devised in 1806.

There were though other scales already in existence, including those used by the likes of Daniel Defoe and Colonel Capper. The Beaufort Scale was the one that got widely disseminated. This spread was helped as Beaufort would become a senior member of the admiralty given the title of British Admiralty Hydrographer of the Navy, as well as becoming a member of the Royal Society, Royal Observatory and the Royal Geographical Society.

Thirty years after Beaufort had first used his devised scale, Captain Beaufort was involved in the commissioning and equipping of HMS Beagle, which was to be under the command of his friend Robert Fitzroy. Beaufort provided Fitzroy with an updated version of his initial scale to use on the voyage to South America in 1836. Within two years the revised scale was made mandatory for all vessels within the Royal Navy, and for the first time there were standard observations being made across the fleet. This standardisation would help to ensure that wind conditions reported by two different people were more like to be the same rather than being subjective.

From the Royal Navy the Beaufort Scale was adopted by merchant vessels, and then to ships around the world.

Today’s version of the Beaufort Scale is an evolved form of the original, and of course observations are no longer made on the sails of naval vessels. Observations today can include sea conditions, estimated wind speeds, open sea wave heights and also expected conditions on land. Despite the technological developments made in the last century, those people providing data to meteorological services around the world still physical observe conditions, rather than read off from gauges.

The Modern Beaufort Scale

0 – Calm; <1mph wind speed; 0ft waves; calm (glassy) sea

1 – Light Air; 1-3mph wind; 0.33ft waves; calm (rippled) sea

2 – Light Breeze; 3-7mph wind; 0.66ft waves; smooth (wavelets) sea

3 – Gentle Breeze; 8-12mph winds; 2ft waves; slight sea

4 – Moderate Breeze; 13-17mph winds; 3.3ft waves; slight-moderate sea

5 – Fresh Breeze; 18-24mph winds; 6.6ft waves; moderate sea

6 – Strong Breeze; 25-30mph winds; 9.9ft waves; rough sea

7 – Near Gale; 31-38mph winds; 13.1ft waves; rough-very rough sea

8 – Gale; 39-46mph winds; 18ft waves; very-rough-high sea

9 – Severe Gale; 47-54mph winds; 23ft waves; high sea

10 – Storm; 55-63mph winds; 29.5ft waves; very high sea

11 – Violent Storm; 64-72mph winds; 37.7ft waves; very high sea

12 – Hurricane; >72mph winds; >45ft waves; phenomenal sea

The Beaufort Scale is of course not the only method for recording wind speeds and sea conditions, and many organisations do record wind speeds in terms of metres per second or equivalent readings. In terms of shipping forecasts though the Beaufort Scale remains an ideal scale for informing those listening of condition out on the sea.

More about this author: Tim Harry

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