|
Beaufort Scale
|
Force |
Description
(specifications to use on land) |
Knots |
Miles per h. |
|
SPECIFICATIONS
FOR USE AT SEA |
0 |
Calm,
smoke rises verticall |
<1 |
<1 |
Sea like a mirror |
1 |
Light air,
direction of wind shown by
smoke drift
|
1/3 |
1/3 |
Ripples with the appearance
of scales are formed, but without foam crests |
2 |
Light Breeze,
wind felt on face; leaves
rustle
|
4/6 |
4/7 |
Small wavelets, still
short, but more pronounced. Crests have a glassy appearance and do not break |
3 |
Gentle Breeze,
leaves and small twigs in
constant motion; wind extends
light flag
|
7/10 |
8/12 |
Large wavelets. Crests
begin to break. Foam of glassy appearance. Perhaps scattered white horses |
4 |
Moderate Breeze,
raises dust and loose paper;
small branches are moved
|
11/16 |
13/18 |
Small waves, becoming
larger; fairly frequent white horses |
5 |
Fresh Breeze,
small trees in leaf begin to
sway; crested wavelets form on
inland waters
|
17/21 |
19/24 |
Moderate waves, taking
a more pronounced long form; many white horses are formed. Chance of some
spray |
6 |
Strong Breeze,
large branches in motion;
whistling heard in telegraph
wires; umbrellas used with
difficulty
|
22/27 |
25/31 |
Large waves begin to
form; the white foam crests are more
extensive everywhere. Probably some spray osse |
7 |
Near Gale,
whole trees in motion;
inconvenience felt when walking
against the wind
|
28/33 |
32/38 |
Sea heaps up and white
foam from breaking waves begins to
be blown in streaks along the direction of the wind |
8 |
Gale,
breaks twigs off trees;
generally impedes progress
|
34/40 |
39/46 |
Moderately high waves
of greater length; edges of crests begin to breakinto spindrift. The foam
is blown in well-marked streaks
along the direction of the wind. |
9 |
Severe Gale,
slight structural damage occurs
(chimney-pots and slates removed)
|
41/47 |
47/54 |
High waves. Dense streaks
of foam along the direction of the wind. Crests of waves begin to topple,
tumble and roll over. Spray may affect visibility |
10 |
Storm,
seldom experienced inland; trees
uprooted; considerable structural
damage occurs
|
48/55 |
55/63 |
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. On the whole the surface of the sea
takes on a white appearance. The 'tumbling' of the sea becomes
heavy and shock-like. Visibility affected |
11 |
Violent Storm,
very rarely experienced;
accompanied by wide-spread damage
|
56/63 |
64/72 |
Exceptionally high waves
(small and medium-size ships might be for a time lost to view behind the
waves). The sea is completely
covered with long white patches of foam lying along the direction
of the wind. Everywhere the edges of the wave crests are blown into froth.
Visibility affected |
12 |
Hurricane,
danni ingentissimi. |
>64 |
>73 |
The air is filled with
foam and spray. Sea completely white with
driving spray; visibility very seriously affected |
