A wind-estimation system developed in 1806 by Admiral
Beaufort of the British Navy. Admiral Beaufort related wind speed
and sea surface
conditions and designed a 0-12 (calm to hurricane)
wind scale with descriptions sea conditions at each level.
Beaufort's scale was adopted by the U.S. Navy
in 1838. Presently,
an adaption of the Beaufort Scale, called the Universal Sea State
Code, is used internationally
and ranges from 0 to 9.
Sea State Code & Description
Sea like a mirror
; wind less than one knot
. Average wave height
s; no foam
; very light winds, 1-3 knots, not felt
on face. Average wave height is from 0-0.3 m (0-1 ft).
sea; small wavelets
; winds light to gentle, 4-6 knots,
felt on face; light flags wave.
Average wave height is 0.3-0.6 m (1-2 ft).
sea; large wavelets, crest
s begin to break; winds gentle
to moderate, 7-10 knots; light flags
fully extend. Average wave height is 0.6-1.2 m (2-4 ft).
sea; moderate waves, many crests break, whitecap
wind-blown spray; winds moderate to
strong breeze, 11-27 knots; wind whistles
in the rigging. Average wave
height is 1.2-2.4 m (4-8 ft).
A very rough sea; waves heap
up, forming foam streaks and spindrift
winds moderate to fresh gale
, 28-40 knots; wind affects walking.
Average wave height is 2.4-4.0 m (8-13 ft).
sea; sea begins to roll, forming very definite
foam streaks and considerable spray
; winds a strong gale, 41-47 knots;
loose gear and light canvas may be blown
about or ripped. Average wave
height is 4.0-6.1 m (13-20 ft).
A very high sea; very high, steep waves with wind driven
crests; sea surface whitens due to dense coverage with foam;
reduced due to wind blown spray; winds at whole gale force,
48-55 knots. Average wave height is 6.1-9.1 m (20-30 ft).
seas; very high-rolling breaking
surface foam covered; very poor visibility; winds at storm level, 56-63
knots. Average wave height 9.1-13.7 m (30-45 ft).
Air filled with foam; sea surface
white with spray; winds
64 knots and above. Average wave height is 13.7 m and above (45 ft and above).
Source: An Introduction to the World's Oceans
. Duxbury, Duxbury & Sverdrup.
McGraw Hill, 2000.