A wind-estimation system developed in 1806 by
Admiral Sir Francis
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
SS0Sea like a
mirror; wind less than one
knot. Average
wave height is
0.
SS1 A
smooth sea;
ripples; no
foam; very light winds, 1-3 knots, not felt
on face. Average wave height is from 0-0.3 m (0-1 ft).
SS2 A
slight 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).
SS3
A
moderate sea; large wavelets,
crests 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).
SS4
A
rough sea; moderate waves, many crests break,
whitecaps, some
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).
SS5
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).
SS6
A
high 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).
SS7 A very high sea; very high, steep waves with wind driven
overhanging crests; sea surface whitens due to dense coverage with foam;
visibility 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).
SS8 Mountainous seas; very high-rolling
breaking waves; sea
surface foam covered; very poor visibility; winds at storm level, 56-63
knots. Average wave height 9.1-13.7 m (30-45 ft).
SS9 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.