Historical and Contemporary Versions of the Beaufort Scale

About this page

Preamble

The Beaufort Scale, used throughout the marine world, has developed over many years. How the scale is defined depends, to some extent, on the user. This page puts Beaufort into historical context and shows how the ideas have different applications.

Related pages

• * How the Beaufort scale came into being and why it is still a useful tool
• Is it better to measure or estimate wind strength?
• Why do we need a Beaufort Scale?
• Visibility measurement at sea
• Single Observer Forecasting.

On this page

• Pre Beaufort
• Beaufort's Original
• Evolution of the scale
• Beaufort's Final
• Beaufort Today
• Dinghy Version
• Coarse Sailors
• Cruising version
• Beaufort Philosophy
• Self calibration

The history pre Beaufort.

In 1704, after he had witnessed the Great Storm of 1703, Daniel Defoe suggested a scale of winds comprising 11 points and using words normally used in the English language. Even before that, certainly during the late 17th century sailors were using a fairly standard set of names to describe winds. In a book written in 1697 after a circum-navigation, it is clear that William Dampier, the Privateer, was using the same general words to describe winds.

In 1759, John Smeaton, a British civil engineer designed an early anemometer as part of his study into windmill design. From readings with this and his experiments he defined an 8 point scale of winds. This had descriptions in terms of movement of leaves, branches and trees as well as the speed of rotation of a windmill. Some 20 years later, Alexander Dalrymple, Hydrographer of the Honourable East India Company, with which Beaufort had served his sea going apprenticeship, produced a scale of winds for use by company captains. A very similar words were used by Archibald Menzies on Vancouver's circumnavigation from. 1791 to 1795.

In 1801, Colonel Capper, also of the Honourable East India Company, calibrated a list of he common terms in terms of miles per hour and feet per second. Apart from Smeaton and Capper, nobody else seems to have tried to define the terms used in ship's logs to describe wind. Even Dalrymple seems to have taken it for granted that his captains would all work to a c common, but unwritten standard. When, on 13th January, 1806, Commander Francis Beaufort of His Majesty’s Sloop Woolwich wrote in his logbook that he would use a 0 - 13 point scale to which he gave descriptive names, he was only following the custom of the sea at that time. Not surprisingly, Beaufort was highly influenced by Dalrymple and, in his 1806 scale he used very similar descriptive names but added an extra, fifth, point which he called a “Moderate Breeze". It is clear that Beaufort was being evolutionary rather than revolutionary.

The evolution of the Beaufort scale

The real and very significant contribution of Beaufort came in 1810 when, now as captain of His Majesty’s Sloop Blossom, he defined, in his logbook, the sea going characteristics of each point on his scale. His definitions are unlikely to be original in that he was, no doubt, reflecting collective marine experience of the time. Beaufort showed great foresight in recognising the need for a standard and uniformly applied wind scale. In this respect, his scale has been and continues to be of great value to both operational meteorology and, importantly in these days of climate change concerns, also to climatology.

Following discussion with Captain Fitzroy of HMS Beagle, and others, Beaufort refined the scale, now the 0 to 12 points version that rightly bears his name. In 1831 he submitted it to his seniors for official approval and in 1838 it was accepted by their Lordships of the Admiralty as the definitive scale to be used by all ships of the Royal Navy (Table 2). In 1854, Fitzroy, another great sailor, navigator and innovator, formed, and became the first Secretary of, the Meteorological Department of the Board of Trade, later the Meteorological Office.

Each force from 1 - 4 was described by Beaufort in terms of the speed of a man-of-war under full sail on her fastest point of sailing – “clean full.” This would correspond to the broad reach of a modern sailing yacht with the wind some 120 degrees off the bow. For forces 5 to 11 he used descriptions relating to the amount of sail that she could carry when “in chase, full and by”. That meant when the captain was carrying as much sail as possible in order to catch the enemy but without masts or spars being carried away. Clearly, this was a matter of very fine judgement; carry too little sail and the enemy would escape; too much sail and the same result would ensue. Neither would enhance the reputation or career prospects of the captain.

For a modern yacht, the equivalent of “full and by” would, most probably, be a fine reach or a close hauled course with the wind some 40 degrees off the bow. A square rigged vessel of the time might manage up to between 60 and 70 degrees off the bow. Even a sloop, like those commanded by Beaufort could do little better. For a modern sailing yacht, as for a ship of Beaufort’s time, the amount of sail carried has a critical effect on the performance of the boat.

This is most evident when racing when there is, again, a fine balance between carrying so much sail that the yacht is heeling too much for optimum speed, or even suffers gear failure, and so little that opponents sail a faster course to the next mark of the course. Neither wins races.

The strongest wind, a force 12, was defined by the immortal phrase “That which no canvas could withstand.” In survival conditions, Beaufort saw no need to differentiate between higher strengths of wind. Modern versions of the Beaufort scale have higher numbers but, although important meteorologically, these are as irrelevant to the skipper of a sailing vessel now as they would have been 200 years ago. For a small vessel, any hurricane represents survival conditions. Even for a large ship, a force 12 or higher is extremely hazardous. The single word “hurricane” is quite sufficient in any forecast to draw attention to the severity of the expected conditions.

Beaufort defined his scale for a man of war and the definitions would not necessarily suit every ship of the time. However. experienced sailors would recognise the terms used and be able to give a wind force in a reasonably consistent manner.

Beaufort Today

For reasons outlined on the page Why Do We Need The Beaufort Scale? the observing of wind by the Officer of the Watch on board a merchant ship is usually by reference to the state of the sea. The current Beaufort scale, and a land version follows. The land version is to help observers who do not have properly sited anemometers to report the wind force.

A Dinghy Sailor's Scale.

There are, of course, other versions of the Beaufort Scale. In the early 70s, the Heron Dinghy Class had its own set of definitions as follows.

In our days of sailing Fireflies, we knew that we could plane at the high end of a Force 3. No doubt, other classes will have their bench marks,

A Coarse Sailor's Scale

In Wind in the Willows, Toad of Toad Hall described sailing as mucking about in boats. On the other hand, Michael Green in his wonderfully, apocryphal book, The Art of Coarse Sailing defined sailing on the Broads as boating about in the muck. In this book and very much in keeping with the general tenor he defined the Coarse Sailor's Beaufort scale as follows -

In Dieppe one of my correspondents saw Météo France cards in the Capitainerie. On the back of these cards was a definition of the Beaufort scale including Force 9 and above - "Les enfants moins de six ans volent" - "If children less than 6 years old fly". Even Michael Green would have been proud of that one!

Along the same lines and thanks to another of my contacts, I can offer the following, attributed to Geoffrey Ball, Sutton Coldfield,

A Cruising Yachtsman's Scale

More recently, a firm of riggers produced the following versions -

The Philosophy of the Beaufort Scale

Clearly there will be variations on the definitions depending upon the yacht, its crew and their recent lifestyle. A Hallberg Rassy 42 would have different rigs for the various wind forces from, say, a small, light yacht such as a Jeanneau 30. A fit, young, strong crew may keep more sail than a retired couple who simply want a comfortable sail and are not concerned about speed.

All the versions of the Beaufort Scale, from the original 1810 version right through the jokey Michael Green versions to the serious and semi-serious Atlantic Spars versions have a common feature.

They all relate the wind to its effects on boats, the sea, people and the world around us. It is that that makes the Beaufort Scale still the most appropriate way to describe wind in weather forecasts for seafarers. There are other reasons. First, the wind is never constant and it is tedious to have to write and listen to an expected wind speed as a range of knots. Secondly, it helps clarity when hearing a forecast to have one or two words clearly enunciated rather than a phrase. Thirdly, the use of the Beaufort Scale does remind us, should we need reminding, that what matters to us is the effect of the wind rather than some number of knots.

Calibrating yourself

The sailor can, of course, check his estimates of the wind force by reference to his measured apparent wind speed. This is best taken using a mast head instrument but a hand held anemometer will suffice. Strictly speaking the hand-held measurements should be corrected for height in order to replicate the masthead reading but this is probably not necessary bearing in mind the various errors in observation. In order to calculate the true wind speed allowance has to be made for the speed of the yacht. This can be done graphically using the triangle of velocities method or by using the mathematical version, the cosine rule.

If you have a VMG display, then it is a simple matter to subtract the VMG value from the indicated wind when going upwind. Going downwind, add the VMG value to the indicated, relative, wind speed. This can become painfully obvious when running downwind and flying a spinnaker when short-handed. It is all too easy to be enjoying tramping along at 7 or eight knots but then suddenly realise that the relative wind has crept up to 15 knots and that the true wind must be around the bottom of Force 6.

Frightening for a cruising yacht skipper but delight to a racing crew.

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