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THE DOUGLASS SEA FORCE SCALE
 
 

 

Sir Henry Percival Douglass

Velocity Equivalent in...
grade Beaufort type of wind knots km/h m/sec grade Douglass
0

calm

< 1
< 1
< 0,2
0
1

puff of wind

1 - 3
1 - 5
0,3 - 1,5
1
2

light breeze

4 - 6
6 - 11
1,6 - 3,3
2
3

breeze

7 - 10
12 - 19
3,4 - 5,4
2
4

lively breeze

11 - 16
20 - 28
5,5 - 7,9
3
5

stiff breeze

17 - 21
29 - 38
8,0 - 10,7
4
6

fresh wind

22 - 27
39 - 49
10,8 - 13,8
5
7

moderate gale

28 - 33
50 - 61
13,9 - 17,1
6
8

moderate squall

34 - 40
62 - 74
17,2 - 20,7
7
9

strong squall

41 - 47
75 - 88
20,8 - 24,4
7
10

tempest

48 - 55
89 - 102
24,5 - 28,4
8
11

storm

56 - 63
103 - 117
28,5 - 32,6
9
12

hurricane

64 e oltre
118 e oltre
32,7 e oltre
9

The Beaufort Scale determines the sea condition in base to the wave's medium height, so, it's not exact to proclaim this Scale as “force”, while is fairly referred only to the wind.

State of the Sea
κατάσταση της θάλασσας (GR) state of the sea (GB) etat de la mer (FR) estado del mar (E) stato del mare (IT) middle height of the waves
άπνοια
calm/glassy
calm
calma
calmo
σχεδόν άπνοια
calm/rippled
calm/ridèe
calma-rizada
quasi calmo
0 - 0,10
ασθενής
smooth
belle
marejadilla
poco mosso
0,10 - 0,50
σχεδόν μέτριος
slight
peu agitèe
marejada
mosso
0,50 - 1,25
μέτριος
moderate
agitèe
fuerte marejada
molto mosso
1,25 - 2,50
ισχυρός
rough
forte
gruesa
agitato
2,50 - 4
σχεδόν θυελλώδης
very rough
très forte
muy gruesa
molto agitato
4 - 6
πολύ θυελλώδης
high
grosse
arbolada
grosso
6 - 9
θύελλα
very high
très grosse
montañosa
molto grosso
9 - 14
τυφώνας
phenomenal
enorme
enorme
tempestoso
14 και άνω

The Douglas Scale of the state of the sea, has been created by the English Admiral H.P. Douglas in 1917 while he was chief of the Meteorological Service of the British Marine and is used in navigation for the valuation of the “wind sea” hight and of the “swell”. Since 1929, the Douglas Scale has been adopted by the International Meteorological Conference of Copenhagen.

wind sea/mer du vent/mar de viento/mare vivo/Ζωντανή θάλασσα

The wind sea is the wave movement generated directly by the wind in action in the observed sea area or in the immediate vicinity.

swell/houle/mar de leva/mare morto/Νεκρή θάλασσα

The swell is the wave coming from remote gale areas (onde lunghe) or from those still residual of the waters where blowed a very strong wind (onde morte). 

Short Wave

0 - 100 metres

Average Wave

100 - 200 metres

Long Wave

over 200 metres



Low Wave

0 - 2 metres

Moderate Wave

2 - 4 metres

High Wave

over 4 metres