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Beaufort
Number
Wind
Velocity
(Knots)
(MPH) Sailorís
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.