(Beaufort) Common Wind Speed Scale (Year of 1906)

force 0	(calm)	0 kn.	Sea: like a mirror
force 1	(light air)	1 - 3 kn.	Sea: ripples with appearance of scales, no foam crests
force 2	(light breeze)	4 - 6 kn.	Sea: small wavelets, crests of glassy appearance, not
			breaking
force 3	(gentle breeze)	7 - 10 kn.	Sea: large wavelets, crests begin to break, scattered whitecaps
force 4	(moderate breeze)	11 - 16 kn.	Sea: small waves, becoming longer, numerous whitecaps
force 5	(fresh breeze)	17 - 21 kn.	Sea: moderate waves, taking longer form, many whitecaps,
			some spray
force 6	(strong breeze)	22 - 27 kn.	Sea: larger waves forming, whitecaps everywhere, more spray
force 7	(moderate gale)	28 - 33 kn.	Sea: sea heaps up, white foam from breaking waves begins to
			be blown in streaks
force 8	(fresh gale)	34 - 40 kn.	Sea: moderately high waves of greater length, edges of crests
			begin to break into spindrift, foam is blown in well-marked
			streaks
force 9	(strong gale)	41 - 47 kn.	Sea: high waves, sea begins to roll, dense streaks of foam,
			spray may reduce visibility
force 10	(whole gale)	48 - 55 kn.	Sea: very high waves with overhanging crests, sea takes white
			appearance as foam is blown in very dense streaks, rolling is
			heavy & visibility is reduced
force 11	(storm)	56 - 63 kn.	Sea: exceptionally high waves, sea covered with white foam
			patches, visibility further reduced
force 12	(hurricane)	64 - 71 kn.	Sea: air filled with foam, sea completely white with driving
			spray, visibility greatly reduced

force 13	(hurricane)	72 - 80 kn.	Sea:	(Yr.1946)
force 14	(hurricane)	81 - 89 kn.	Sea:	(Yr.1946)
force 15	(hurricane)	90 - 99 kn.	Sea:	(Yr.1946)
force 16	(hurricane)	100 - 108 kn.	Sea:	(Yr.1946)
force 17	(hurricane)	109 - 118 kn.	Sea:	(Yr.1946)
•

The common wind speed scale for seafarers is no more than a guide to show roughly what may be expected

on the open sea, remote from land. It applies only when the sea is fully developed; that is, when waves have

reached their maximum height for a particular wind speed. Care must be exercised when the fetch and

duration of the wind are limited. Also remember that the appearance of the sea's surface is influenced not only

by wind but also by swell, precipitation, tidal streams and other currents in the sea.

•

force 0	(calm)	0 stt.ml.	Land: smoke rises vertically
force 1	(light air)	1 - 3 stt.ml.	Land: smoke drifts slowly downwind
force 2	(light breeze)	4 - 7 stt.ml.	Land: leaves rustle
force 3	(gentle breeze)	8 - 12 stt.ml.	Land: leaves are in motion
force 4	(moderate breeze)	13 - 18 stt.ml.	Land: small branches on trees move
force 5	(fresh breeze)	19 - 24 stt.ml.	Land: small trees sway
force 6	(strong breeze)	25 - 31 stt.ml.	Land: large branches sway
force 7	(moderate gale)	32 - 38 stt.ml.	Land: whole trees in motion
force 8	(fresh gale)	39 - 46 stt.ml.	Land: twigs & small brances break off trees
force 9	(strong gale)	47 - 54 stt.ml.	Land: large branches break off trees, slight structural damage
force 10	(whole gale)	55 - 63 stt.ml.	Land: trees broken, minor structural damage
force 11	(storm)	64 - 72 stt.ml.	Land: widespread damage
force 12	(hurricane)	73 - 82 stt.ml.	Land: violent movement of trees & much destruction

force 13	(hurricane)	83 - 92 stt.ml.	Land:	(Yr.1946)
force 14	(hurricane)	93 - 103 stt.ml.	Land:	(Yr.1946)
force 15	(hurricane)	104 - 114 stt.ml.	Land:	(Yr.1946)
force 16	(hurricane)	115 - 125 stt.ml.	Land:	(Yr.1946)
force 17	(hurricane)	126 - 136 stt.ml.	Land:	(Yr.1946)
•

Limits of wind speed at 5 fathoms above sea, or above land

Resolution 9, International Meteorological Committee, Paris, Yr.1946

LEATHER SEALER'S OFFICE, Londonderry, Vt.

April 8th 1826

Rory Ely Cole

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