| Beaufort Number |
Wind Velocity (Knots) |
(MPH) | Sailor’s Term |
Sea Condition | *Typical WaveHeight Feet |
**Typical Attainment Time |
|
0
|
0-1
|
0-1.7
|
Calm
|
Glassy-smooth,
mirror-like
|
Smooth
|
-
-
|
|
1
|
2-3
|
1.8-4.0
|
Light
air
|
Scale-like
ripples
|
Ripples
|
1-10
min.
|
|
2
|
4-6
|
4.1-7.4
|
Light
breeze
|
Small,
short wavelets with glassy crests
|
1/3
|
5-15
min.
|
|
3
|
7-10
|
7.5-12.0
|
Gentle
breeze
|
Large
wavelets, crests begin to break, occasional form
|
1-2
|
5-20
min.
|
|
4
|
11-16
|
12.1-18.9
|
Moderate
breeze
|
Small
waves, some whitecaps, more frequent form
|
2-3
|
15-60
min.
|
|
5
|
17-21
|
19.0-24.7
|
Fresh
breeze
|
Moderate
longer waves, better formed, many whitecaps, much foam, some spray
|
3-4
|
15-60
min.
|
|
6
|
22-27
|
24.8-31.6
|
Strong
breeze
|
Large
waves form, many whitecaps, foam everywhere, more spray
|
4-5
|
1/4-2
hr.
|
|
7
|
28-33
|
31.7-38.5
|
Moderate
gale
|
Sea
heaps up, streaks of foam spindrift begins
|
5-6
|
1/2-3
hr.
|
|
8
|
34-40
|
38.6-46.6
|
Fresh
gale
|
Moderately-high
long waves, crests into spindrift, well-marked streaks of foam
|
6-7
|
1/2-3
hr.
|
|
9
|
41-47
|
46.7-53.9
|
Strong
gale
|
High
waves, sea rolls, dense streaks, spray affects visibility
|
7-8
|
1/2-4
hr.
|
| * | Wave height is dependent on water depth and length of time that the wind has been blowing. These are typical heights for lakes, bays and estuaries. The above conditions and wave heights should prevail after the attainment times indicated. Large numbers of powerboats on enclosed bodies of water should be considered when estimating wave heights. | |||||
| ** | These attainment times are for winds of constant or increasing intensities. For decreasing intensities, surface characteristics will have to be relied upon; for example, one-foot glassy-smooth waves still indicate Beaufort # = 0 wind conditions. | |||||