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Beaufort Scale

Admiral Francis Beaufort was a 19^th century British tar in the days of the old wooden tall ships. The scale he developed has been ridiculed by mariners for being patternless because there is no apparent uniform progression in the scale. Force 2, for example, describes winds from 4 to 6 knots, Force 3 from 7 to 10, and Force 4 from 11-16. Then Force 5 covers only from 17-21. The wind differences vary from 2 knots to 3, then 5, and back to 4.

Part of our Pacific Bliss library contains a book called Mariner's Weather by William P. Crawford. He claims that the lack of symmetry was not part of Beaufort's plan, and defends his damaged reputation by saying that the Admiral was not referring to wind speed at all! He says that what the esteemed Admiral had in mind was the number of sails that should be furled as the wind strengthened. In light airs, just one would be taken in, whereas in a gentle breeze might require three. In a near gale, seven would come down, and in a violent storm, eleven.

There is now a tendency to express wind value in knots instead of Beaufort scale. The Pacific Bliss multi units allow the user to choose whichever he or she wishes as a display. We use the Force scales in the cockpit display. A read-out in knots suggests a misleading exactness whereas a Force reading allows for the slack. It makes it easier to give instructions to the crew; for example, during the Atlantic crossing, instructions were to take down the spinnaker at Force 7.

The following chart will help you understand the forces and sea conditions we encountered during our night of sheer terror:

Beaufort Scale: Comparing Wind Speed and Sea Conditions
Force	Knots	Probable Weight Height	Description	Sea Conditions
0	0-1	--	Calm	Sea smooth and mirror like
1	1-3	1/4	Light Air	Scale-like ripples without foam crests
2	4-6	1/2	Light Breeze	Small, short wavelets; some crests begin to break; foam of glassy appear- ance. Occasional white foam crests.
3	7-10	2	Gentle Breeze	Large wavelets; some crests begin to break; foam of glassy appearance. Occasional white foam crests
4	11-16	4	Moderate Breeze	Small waves, becoming longer; fairly frequent white foam crests
5	17-21	6	Fresh Breeze	Moderate waves, taking a more pro- nounced long form, many white foam crests; there may be some spray
6	22.27	10	Strong Breeze	Large waves begin to form; white foam crests are more extensive everywhere; there may be some spray
7	28-33	14	Near Gale	Sea heaps up and white foam from breaking waves begins to be blown in Streaks along the direction of the wind; spindrift begins.
8	34-40	18	Gale	Moderately high waves of greater length; edges of crests break into spindrift; foam is blown in well-marked streaks along the direction of the wind.
9	41-47	23	Strong Gale	High waves; dense streaks of foam along the direction of the wind; crests of waves begin to topple, tumble, and roll over; spray may reduce visibility
10	48-55	29	Storm	Very long waves with overhanging crests. The resulting foam in great patches is blown in dense white streaks along the direction of the wind. On the whole, the surface of the sea is white in appearance. The tumbling of the sea becomes heavy and shocklike. Visibility is reduced.
11	56-63	37	Violent	Exceptionally high waves that may obscure small and medium size ships. The sea is completely covered with long white patches of foam lying along the direction of the wind. Everywhere the edges of the wave crests are blown into froth.Visibility reduced.
12	64-71	45	Hurricane	The air is filled with foam and spray. Sea completely white with driving spray; visibility much reduced.

Source: From the Weather Bureau Observing Handbook No. 1, Marine Surface Observations (Wash. D.C. National Weather Service, 1969)

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