| Beaufort Force # |
Speed
(Measured at 10 m above ground) |
Description |
Effects |
| mph |
km/hour |
knots |
on
land |
on
sea |
| 0 |
<1 |
<1 |
<1 |
Calm |
Still, calm air;
smoke will rise vertically. |
Water is
mirror-like. |
| 1 |
1-3 |
1-5 |
1-3 |
Light Air |
Rising smoke
drifts; still wind vanes. |
Small ripples
appear on water surface, but without foam crests. |
| 2 |
4-7 |
6-11 |
4-6 |
Light Breeze |
Leaves rustle,
can feel wind on your face, wind vanes begin to move. |
Small wavelets
develop, crests are glassy and do not break. |
| 3 |
8-12 |
12-19 |
7-10 |
Gentle Breeze |
Leaves and small
twigs move, light weight flags extend. |
Large wavelets,
crests start to break, some whitecaps (white horses). |
| 4 |
13-18 |
20-28 |
11-16 |
Moderate Breeze |
Small branches
move; raises dust, leaves and paper. |
Small waves
develop (1-4 feet), becoming longer; whitecaps (white horses). |
| 5 |
19-24 |
29-38 |
17-21 |
Fresh Breeze |
Small trees sway;
crested wavelets form on inland waters. |
White crested
wavelets (whitecaps) form (4-8 feet), some spray. |
| 6 |
25-31 |
39-49 |
22-27 |
Strong Breeze |
Large tree
branches move, telephone wires begin to "whistle", umbrellas are difficult to
keep under control. |
Larger waves form
(8-13 feet), whitecaps prevalent, spray. |
| 7 |
32-38 |
50-61 |
28-33 |
Near Gale |
Large trees sway,
becoming difficult to walk. |
Larger waves
develop (13-20 feet), white foam from breaking waves begins to be blown. |
| 8 |
39-46 |
62-74 |
34-40 |
Gale |
Twigs and small
branches are broken from trees, walking is difficult. |
Moderately large
waves (13-20 feet) with greater length and blown foam. |
| 9 |
47-54 |
75-88 |
41-47 |
Strong Gale |
Slight damage
occurs to buildings, shingles are blown off of roofs. |
High waves (20
feet / 6 meters), rolling seas, dense foam, blowing spray reduces visibility. |
| 10 |
55-63 |
89-102 |
48-55 |
Storm |
Trees are broken
or uprooted, building damage is considerable. Seldom experienced inland. |
Large waves
(20-30 feet / 6-9 meters), overhanging crests, sea becomes white with foam, heavy rolling,
reduced visibility. |
11 |
64-72 |
103-117 |
56-63 |
Violent Storm |
Extensive
widespread damage. Very rarely experienced. |
Large waves
(30-45 feet / 9-14 meters), white foam, visibility further reduced, small and medium ships
periodically lost to view behind waves. |
| 12 |
73+ |
118+ |
64+ |
Hurricane |
Extreme
destruction, devastation. |
Large waves over
45 feet / 14 meters, air filled with foam, sea white with foam and driving spray, little
visibility at all. |
