BFT-
NAME
FORCE
The Beaufort Scale
WINDSPEED
APPEARANCE OF THE SEA
/KNOT
0
Calm
<1
Sea like a mirror
1
Light Air
1-3
Ripples with the appearance of scales are formed, but without foam
crests
2
Light
4-6
Breeze
3
Gentle
glassy appearance and do not break
7-10
Breeze
4
Moderate
Small wavelets, still short but more pronounced. Crests have a
Large wavelets. Crests begin to break. Foam of glassy appearance.
Perhaps scattered white horses
11-16
Small waves, becoming longer, fairly frequent white horses
17-21
Moderate waves, taking a more pronounced form, many white hors-
Breeze
5
Fresh
Breeze
6
Strong
es are formed. Chance of some spray
22-27
Breeze
7
Near Gale
Large waves begin to form, the white foam crests are more extensive everywhere. Probably some spray
28-33
Sea heaps up and white foam from breaking waves begins to be
blown in streaks along the direction of the wind
8
Gale
34-40
Moderately high waves of greater length; edges of crests begin to
break into spindrift. The foam is blown in well marked streaks along
the direction of the wind
9
Severe
41-47
Crests of waves begin to topple, tumble and roll over. Spray may
Gale
10
Storm
High waves. Dense streaks of foam along the direction of the wind.
affect visibility
48-55
Very high waves with long over hanging crests. The resulting foam
in great patches is blown in dense white streaks along the direction
of the wind. Surface of the sea takes on a white appearance. The
“tumbling” of the sea becomes heavy and shock-like. Visibility
affected.
11
Violent
56-63
Storm
Exceptionally high waves (small and medium sized ships might be
lost for a time behind the waves). The sea is completely covered
with long white patches of foam lying along the direction of the
wind.
12
Hurricane
64
The air is filled with foam and spray. Sea completely white with
driving spray, visibility seriously affected.
50