|
Judging the Strength of the Wind & The
Beaufort Scale
 A number of devices are available to measure wind speed they cost between $100 and $150.
They are very useful in teaching one to judge the wind by the appearance
of the seas. By vision the best signs are white caps and foam
in streaks. Frequent white caps form at 10 knots and foam in streaks
at 28 knots. The decision of when reef is dependent upon the
sailboat design and the wind conditions. The best indicators are too
much heel and too much weather helm. In most sailboats, if there are many white caps the
wind is probably enough to place one reefing point. Extensive white
caps with spray, indicates winds which may require at least two
reefing points. Small sailboats or
inexperienced sailors should not be out in such conditions.
* Wave height is only a rough estimate.
Wave height is determined by three factors, wind speed, duration the wind
has been blowing and the fetch, or distance, the wind blows over a body of
water.
Below is a description
of the Beaufort Scale: For further information and an excellent
history of the Beaufort Scale go to
http://www.crh.noaa.gov/lot/webpage/beaufort/
Whitecaps: Foam crests on the top
of waves. Spray: Water blown off the top of waves.
Spindrift: heavy spray
Wind Strength
(Knots) |
Sea
Appearance |
Wind
Description |
Wave Height*
(feet) |
Beaufort Scale
(Force) |
Force on Sails
(lbs per sq foot) |
|
0 |
like glass |
Calm |
0 |
0 |
|
|
1-3 |
small ripples |
Light Air |
1/4 - 1/2 |
1 |
0.02 |
|
4-6 |
small wavelets
some crests |
Light Breeze |
1/4 - 1/2 |
2 |
0.11 |
|
7-10 |
larger wavelets
rare whitecaps |
Gentle Breeze |
2 |
3 |
0.31 |
|
11-16 |
small waves
some whitecaps |
Moderate Breeze |
3 |
4 |
0.79 |
|
17-21 |
frequent whitecaps, some spray |
Fresh Breeze |
6 |
5 |
1.56 |
|
22-27 |
large waves, some spray,
many whitecaps |
Strong Breeze |
10 |
6 |
2.59 |
|
28-33 |
white foam starting to form
streaks, breaking waves |
Near Gale |
13 |
7 |
4.01 |
|
34-40 |
breaking waves,
edges of crests breaking into
spindrift,
well marked steaks of foam |
Gale |
18 |
8 |
5.90 |
|
41-47 |
High waves with dense foam
steaks, some waves rolling over, visibility reduced by spray |
Strong Gale |
22 |
9 |
8.34 |
|
48-55 |
Very high waves. The whole sea looks white,
decreased visibility, waves rolling over with force
|
Storm |
29 |
10 |
11.43 |
|
56-63 |
Huge waves, all wave edges are
blown into froth, patches of foam covers the sea |
Violent Storm |
37 |
11 |
15.26 |
|
64-71 |
The air is covered with foam
and spray, the sea is completely white, enormous waves. |
Hurricane |
45 |
12 |
19.64 |
Number of hits as of
12/30/2001
Page Last Updated
04/10/2003 |
