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The Beaufort Wind Scale

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Ever wondered what 'Wind force 12 abaft the beam' actually means? The term 'wind force' and the scale used to measure the speed1 of the wind were devised in 1805 by British Navy Admiral Sir Francis Beaufort2 (1774 - 1857). Beaufort developed the scale by measuring the effect the wind had on the flags and sails of the HMS Woolwich. In 1829, Beaufort was appointed Hydrographer to the Admiralty, and in 1838, his 'Wind Force Scale' was introduced by the British Navy for use in log entries.

The original Beaufort scale stayed in use until 1905, when Sir George Simpson adapted the scale to modern steamships. In 1921, the International Meteorological Committee (now defunct) approached Sir George to develop a new wind scale, acceptable by all nations. He included indications which were easier to understand for the shore-based part of mankind, such as ascending smoke, leaves rustling and the swishing of trees. He also added measured wind speeds to the scale3.

By now, one may be thinking, 'This is all very well and good, but how does it affect me?' Firstly, one may use the scale to determine the day's surfing conditions. In the calm of force 0, the sea is mirrorlike. By the fresh gale of force 8, long strings of foam appear on the ocean, and waves can be 13 to 20 feet high4. Secondly, scientists and engineers use the scale to find areas where wind-powered generators may be built5. Thirdly, some people may have foreign-made furnishings in his or her home or work place. How do you suppose those furnishings came to be in almost every little part of the world? The answer is cargo ships! The daily shipping news is important to many companies that trade overseas. Finally, and most obviously, one can use the scale to determine key factors of the weather, and the weather forecasts all over the world use the Beaufort scale to inform you what the wind will be.

For all the do-it-yourselfers out there, here is Sir George Simpson's version of the Beaufort Wind Scale6:

Wind Force NumberDescriptionSpeed in Miles per HourSpeed in Kilometres per HourSpeed in KnotsObservation
0Calm0-10-1calmSmoke rises vertically
1Light Air1-31-5calmSmoke drifts slowly
2Slight Breeze4-76-115 knotsWind felt on face; leaves rustle; flags stir
3Gentle Breeze8-1212-1910 knotsLeaves and twigs in constant motion; wind extends light flags
4Moderate Breeze13-1820-2915 knotsDust and small branches move; flags flap
5Fresh Breeze19-2430-3920 knotsSmall trees with leaves begin to sway; flags ripple
6Strong Breeze25-3140-4925 knotsLarge branches move; flags beat
7Moderate Gale32-3850-6130 knotsWhole trees move; flags extended
8Fresh Gale39-4662-7435 knotsTwigs break off trees; walking is hindered
9Strong Gale47-5475-8845 knotsSlight damage to houses (such as slates removed)
10Whole Gale55-6389-10250 knotsTrees uprooted; much damage to houses
11Storm64-72103-11760 knotsWidespread damage
12Hurricane73-82118-13470 knotsExcessive damage

A Few More Wind Speed Fun Facts

A sneeze can travel as fast as 100 miles per hour. The fastest ever recorded was 103.6 mph. A cough, by the way, produces air travelling upwards of 60 mph.

Hurricane Andrew, which devastated Homestead, Florida City, and the surrounding area in 1992, was Florida's most devastating hurricane and the costliest natural disaster in American history at that time.

The hurricane of 1938 ripped through New York, New England, and Canada, packing wind gusts as high as 186 mph. The damage report included 700 people killed, 63,000 people homeless, an estimated 2 billion trees destroyed and 750,000 chickens killed.

Doldrums are equatorial belts of calm around the earth, centred slightly north of the equator between the two belts of trade winds. The doldrums are noted for calms, periods when the winds disappear, trapping sailing vessels for days or weeks. However, hurricanes originate in this region of low pressure and high humidity.

The Horse Latitudes are two belts of latitude at about 30° where winds are light and the weather is hot and dry. The term 'horse latitudes' supposedly originates from Spanish sailing vessels that transported horses to the West Indies, often becoming becalmed in mid-ocean in this latitude. Prolonged voyages resulted in water shortages that would make it necessary for crews to throw their horses overboard.

1Speed = (Distance / Time).2Beaufort Sea, named after the Admiral, is part of the Arctic Ocean extending from the eastern side of Point Barrow all the way to Banks Island at the edge of the Canadian Arctic Archipelago. Wow, that's a really useless bit of trivia!3Scientists measured the fastest wind speed ever recorded, 318 mph, in one of the tornadoes that hit the suburbs of Oklahoma City on 3 May, 1999 occurring at about 7pm near Moore, where the tornado killed four people and destroyed about 250 houses.4The size of shore waves is highly dependent on the angle of the wind and shore, the shape of the sea bed and sea currents though.5Any wind over force 3 (8 mph) can be used to generate electricity. Currently, though, it only makes economic sense to build wind turbines in areas where the wind has at least force 4 (15 mph) most of the time. Annoy your friends with that little nugget of joy.6A more complete scale for land and sea can be found here.

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