The power of the wind is a force to be reckoned with even today, whether on land or at sea, with gentle breezes refreshing our hot summer days or driving wind turbines and storms threatening to bring down power lines or drive oil tankers ashore. From the very earliest times, people must have had terms to describe the strength of the wind, but there seem to be no records of these surviving. The Beaufort Scale, whilst not the first of its type therefore, proved to be the most detailed and practical and has endured down to the present day, with some modifications.
The Beaufort Scale takes its name from Admiral Sir Francis Beaufort, 1774-1857. He was born in Ireland and went to sea with the Royal Navy in 1787. He rose to command HMS Woolwich in 1805 and it was soon after, in 1806, that he set out in his private Log the outline of 13 scales of increasing wind speed, from ‘Calm’ to ‘Storm’.
We know that something similar had existed at least as early as the beginning of the 1700s. On November 26-7th 1703 Britain had been hit by possibly the most violent storm ever to reach her shores. It had caused widespread devastation. The diligent writer and observer Daniel Defoe described the events and reveals that a 12 point wind scale was already known in his time, ranging from ‘Stark Calm’ to ‘Tempest’. Also surviving are records from the Palatine Meteorological Society of Mannheim in Germany around 1780, giving details of a 4 point scale, ranging from ‘Calm’ to ‘Twigs and branches torn off trees’. By 1801 the East India Company published a ‘table of the different forces and velocities of the winds, constructed by Mr Rous with great care from a considerable number of facts and experiments’.
Francis Beaufort’s scale was the one which came into near universal usage though, and it remains the backbone of wind speed reckoning down to today. Although Beaufort had begun with a 13 point scale in 1806, the very next year he combined points 1 and 2, producing a twelve point scale and he added a useful description of the canvas (sail) that could be carried by a well rigged Frigate:
0……Calm………………………………………………………………….
1……Light air..Just enough to give steerage way……………………………….
2……Light breeze……………Well conditioned…………………………..1-2 knots
3……Gentle breeze…………..Man of war under……………. ………….. 3-4 knots
4…… Moderate breeze………..full sail………………….. ……………5-6 knots
5……Fresh breeze…………Same………………………………………Royals etc
6……Strong breeze………..ship could………………single reefs and top gallants..
7……Moderate gale………..just carry………………..double reefs, jibs etc…….
8……Fresh gale…………….close ………………….triple reefs, courses, etc…
9……strong gale……………hauled …………………close reefs and courses……
10…..Whole gale……….Can only bear close-reefed main tops and reefed foresail…….
11…..Storm……………Reduced to storm staysails……………………………….
12…..Hurricane………..No canvas………………………………………………
This gave Beaufort’s Scale a very important practical use, the more so in an age when ocean going sailing ships were rapidly opening up the sea trade routes of the globe. Although the scale was not made public to begin with, it was used on the famous voyage of HMS Beagle which set out in 1831. This was commanded by Robert Fitzroy, who later became the first Head of the British Meteorological Office. By 1832 Beaufort’s Scale had been published in ‘Nautical Magazine’. In December 1838 the British Admiralty introduced use of the scale into all HM ships and vessels. At this time, Britain’s Royal Navy was by far the largest and most powerful in the world.
With the decline of sail and the rise of steam ships around 1900, modifications were made to the scale to make it more applicable to the new age. A constant was devised, expressed as
V = 1.87xsquare root (B cubed), where V was wind speed and B was the number on the Beaufort Scale. This was in 1903. Three years later, the British meteorologist George Simpson proposed an alternative scale based on the sea’s appearance.
Scales 13-17 were added to the Beaufort Scale in 1944, but these could only be of use in describing tropical storms such as Typhoons and Hurricanes. In 1960 ‘probable average’ and ‘maximum expected’ wave heights were added to the description of each point on the Scale.
Today, when our weather forecasters tell us to expect ‘light to moderate winds’ or ‘strong winds gusting to gale force’ they are referring to a scale which was formalized by Francis Beaufort two hundred years ago; so too when mariners are warned to expect winds of Force 6 to 7. Although modified, the Beaufort Scale is still in use:
Beaufort Scale ..Land.
Force….. MPH…Knots…………………………..Description……………………..
0 Calm 0-1 0-1 Smoke rises vertically……………………………………..
1 Light air 1-3 1-3 Direction of wind shown by smoke drift but not weather vanes……
2 Light breeze 4-7 4-6 Wind felt on face, leaves rustle, weather vanes moved………….
3 Gentle breeze8-12 7-10 Leaves and small twigs in constant motion, light flags extended…
4 Moderate .. 13-18 11-16 Raises dust and loose paper, small branches moved…………….
5 Fresh .. 19-24 17-21 Small trees in leaf begin to sway, crested wavelets from on water.
6 Strong .. 25-31 22-27 Large branches in motion; whistling heard in phone wires; umbrellas
…………………….. used with difficulty.
7 Near Gale 32-38 28-33 Whole trees in motion; inconvenience felt when walking against
………………………wind.
8 Gale 39-46 34-40 Breaks twigs off trees, impedes progress when walking…………
9 Severe Gale 47-54 41-47 Slight structural damage to chimneys and roofs………………
10 Storm 55-63 48-55 Trees uprooted, considerable structural damage to buildings…..
11 Violent storm 64-72 56-63 Rarely experinced, widespread damage……………………..
12 Hurricane 73-83 64-71 .. .. .. ..
Beaufort Scale..Sea.
Force…..(Speeds as above)…………………….Description……………………..
0 Calm…………………Sea like glass………………………………
1 Light Air…………….Ripples like scales, but without foam crests……
2 Light breeze………….Small wavelets, crests glassy and do not break….
3 Gentle breeze…………Large wavelets, crests begin to break, glassy foam
………………………perhaps some white horses…………………….
4 Moderate breeze……….Small waves, becoming larger, fairly frequent white horses
5 Fresh breeze………….Moderate waves, more pronounced long form, many white horses
6 Strong breeze…………Large waves begin to form; white foam crests extensive;
………………………probably some spray.
7 Near Gale…………….Sea heaps up, white foam from breaking waves begins to be
………………………blown in streaks.
8 Gale…………………Moderately high waves of greater length; edges of crests
………………………begin to break into spindrift; blowing foam.
9 Severe Gale…………..High waves, dense streaks of foam; crests of waves start
………………………to topple and roll over; spray may affect visibility.
10 Storm……………….Very high waves with long, overhanging crests; big, blown
………………………foam patches; surface of sea takes on white appearance;
………………………visibility affected.
11 Violent Storm………..Exceptionally high waves; small and medium sized vessels
………………………may be lost to sight; sea covered in foam; edges of waves
………………………blown into froth; visibility affected.
12 Hurricane……………Air filled with foam and spray, sea completely white with
………………………driving spray, visibility severely affected.
