| Beaufort
Number |
Wind
Speed (Knots) |
Wind
Speed (MPH) |
Seaman's
Term |
Effects
observed at sea
|
Effects
observed on land
|
| 0 |
under 1 |
under 1 |
Calm |
Sea like mirror. |
Calm; smoke rises vertically. |
| 1 |
1-3 |
1-3 |
Light air
|
Ripples with appearance of scales; no foam
crests. |
Smoke drift indicates wind direction;
vanes do not move. |
| 2 |
4-6 |
4-7 |
Light breeze |
Small wavelets; crests of
glassy appearance, not breaking. |
Wind felt on face; leaves rustle;
vanes begin to move. |
| 3 |
7-10 |
8-12 |
Gentle breeze |
Large wavelets; crests
begin to break; scattered whitecaps. |
Leaves, small twigs in constant
motion; light flags extended. |
| 4 |
11-16 |
13-18 |
Moderate breeze |
Small waves, becoming
longer form; numerous whitecaps. |
Dust, leaves, and loose paper raised
up; small branches move. |
| 5 |
17-21 |
19-24 |
Fresh breeze |
Moderate waves, taking
longer form; many whitecaps; some spray. |
Small trees in leaf begin to move. |
| 6 |
22-27 |
25-31 |
Strong breeze |
Larger waves forming;
whitecaps everywhere; more spray. |
Larger branches of trees in motion;
whistling heard in wires. |
| 7 |
28-33 |
32-38 |
Moderate gale |
Sea heaps up; white foam
from breaking waves begins to be blown in streaks. |
Whole trees in motion; resistance felt
in walking against the wind. |
| 8 |
34-40 |
39-46 |
Fresh gale |
Moderately high waves of greater
length; edges of crests begin to break into spindrift;
foam is blown in well-marked streaks. |
Twigs and small branches broken off
trees; progress generally impeded. |
| 9 |
41-47 |
47-54 |
Strong gale |
High waves; sea begins to roll; dense streaks of foam;
spray may reduce visibility.
|
Slight structural damage occurs; slate
blown from roofs. |
| 10 |
48-55 |
55-63 |
Whole gale |
Very high waves with overhanging
crests; sea takes white appearance as foam is blown in
very dense streaks; rolling is heavy and visibility
reduced. |
Seldom experienced on land; trees
broken or uprooted; considerable structural damage occurs.
|
| 11 |
56-63 |
64-72 |
Storm |
Exceptionally high waves; sea covered
with white foam patches; visibility still more reduced. |
Very rarely experienced on land;
usually accompanied by widespread damage. |
| 12 |
64-71 |
73-82 |
Hurricane |
Air filled with foam; sea completely
white with driving spray; visibility greatly reduced.
|
Very rarely experienced on land;
usually accompanied by widespread damage. |
| 13 |
72-80 |
83-92 |
Hurricane |
Air filled with foam; sea completely
white with driving spray; visibility greatly reduced.
|
Very rarely experienced on land;
usually accompanied by widespread damage.
|
| 14 |
81-89 |
93-103 |
Hurricane |
Air filled with foam; sea completely white with driving
spray; visibility greatly reduced.
|
Very rarely experienced on land;
usually accompanied by widespread damage. |
| 15 |
90-99 |
104-114 |
Hurricane |
Air filled with foam; sea completely
white with driving spray; visibility greatly reduced. |
Very rarely experienced on land;
usually accompanied by widespread damage. |
| 16 |
100-108 |
115-125 |
Hurricane |
Air filled with foam; sea completely
white with driving spray; visibility greatly reduced. |
Very rarely experienced on land;
usually accompanied by widespread damage. |
| 17 |
109-118 |
126-143 |
Hurricane |
Air filled with foam; sea completely
white with driving spray; visibility greatly reduced. |
Very rarely experienced on land;
usually accompanied by widespread damage. |
