Beaufort Wind Scale
WAVES
WIND SPEED HEIGHT
KM/H M/S KT MPH M FT
0
BF calm 0-1 0-0.2 0-1 0-1 0 0
1
BF light air 1-5 0.3-1.5 1-3 1-3 0.1 0.25
2 0.2-
BF light breeze 6-11 1.6-3.3 4-6 4-7 0.3 0.5-1
3
BF gentle breeze 12-19 3.4-5.4 7-10 8-12 0.6-1 2-3
4 moderate
BF breeze 20-28 5.5-7.9 11-16 13-18 1-1.5 3.5-5
5
BF fresh breeze 29-38 8.0-10.7 17-21 19-24 2-2.5 6-8.5
6 10.8-
BF strong breeze 39-49 13.8 22-27 25-31 3-4 9.5-13
7 13.9- 13.5-
BF near gale 50-61 17.1 28-33 32-38 4-5.5 19
8 17.2- 5.5-
BF gale 62-74 20.7 34-40 39-46 7.5 18-25
9 20.8-
BF strong gale 75-88 24.4 41-47 47-54 7-10 23-32
10 24.5-
BF storm 89-102 28.4 48-55 55-63 9-12.5 29-41
11 103- 28.5- 11.5-
BF violent storm 117 32.6 56-63 64-72 16 37-52
12
BF hurricane >=118 >=32.7 >=64 >=73 14+ 45+
Douglas Sea Scale
This actually has two scales; one for the wind generated waves, and the other for the
background swell. Ideally one should use both scales to fully describe the conditions.
There is a good discussion about the difference between waves and swell on the New
Zealand Met Service Blog.
State of the sea (wind sea)
DEGREE HEIGHT (M) DESCRIPTION
0 no wave Calm (Glassy)
1 0 - 0.10 Calm (Rippled)
2 0.10 - 0.50 Smooth
3 0.50 - 1.25 Slight
4 1.25 - 2.50 Moderate
5 2.50 - 4.00 Rough
6 4.00 - 6.00 Very Rough
7 6.00 - 9.00 High
8 9.00 - 14.00 Very High
9 14.00+ Phenomenal
Swell
DEGREES DESCRIPTION
0 No Swell
1 Very Low (short and low wave)
2 Low (long and low wave)
3 Light (short and moderate wave)
4 Moderate (average and moderate wave)
5 Moderate rough (long and moderate wave)
6 Rough (short and heavy wave)
7 High (average and heavy wave)
8 Very high (long and heavy wave)
9 Confused (wavelength and height indefinable)
Wave length and height classification
Wave length
Short wave 100 m -
Average wave 100 – 200 m
Long wave 201 m +
Wave height
Low wave 2 m -
Moderate wave 2 – 4 m
High wave 4.01 m +
5 THOUGHTS ON “APPENDIX VIII – BEAUFORT WIND AND
The propeller slip is the difference between the speed of the engine and the actual
observed speed of the ship. It is always expressed as a percentage 12. Here are two
formulas to calculate propeller slip:
1. Slip (percent) = Engine distance – ship’s distance/ Engine’s distance X
100 1.
o Engine distance = Pitch X RPM X 60 X 24 / 1852.
o Ship’s distance = 24 X 20.
o For example, if the pitch is 4.5, RPM is 90, then ED = (4.5 X 90 X 60 X
24)/1852 = 314.902. Ship’s distance = 24 X 20 = 480. Therefore, slip =
(314.902-480)/314.902 x 100 = -52.4% 1.
2. Propeller Slip = Actual forward speed/ Theoretical forward speed 2.
o The calculated value of slip will be increased when the wind and sea are
ahead and if the vessel has a fouled bottom 2.
