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The Beaufort Scale

The Beaufort scale was originally invented by Admiral Beaufort in the 1700s. It has been added to and adjusted over the years, giving us the Beaufort scale we use today.

The Beaufort scale helps you to gauge how strong the wind is just by watching how the sea is moved by the wind, or watching how things like trees and smoke are moved by the wind on land. It takes a little practice and experience to learn the scale but once you have it is very useful. You will be able to stand onshore and quickly judge if it is safe for you to venture out.

Many marine forecasts still give the wind's strength using the Beaufort scale. When you hear or read the forecast you will know whether it's worth heading down to the sea or not.

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photo of force 0 at sea

Sea like a mirror. Calm; smoke rises vertically.
Wave height: 0
Knots: < 1
MPH: < 1

photo of force 1 at sea

Ripples with appearance of scales; no foam crests. Direction of wind shown by smoke drift but not by wind vanes.
Wave height: 0-0.2m
Knots: 1-3
MPH: 1-3

photo of force 2 at sea

Small wavelets; crests of glassy appearance, not breaking. Wind felt on face; leaves rustle; vanes moved by wind.
Wave height: 0.2-0.5m
Knots: 4-6
MPH: 4-7

photo of force 3 at sea

Large wavelets; crests begin to break; scattered whitecaps. Leaves and small twigs in constant motion; wind extends light flag.
Wave height: 0.5-1m
Knots: 7-10
MPH: 8-12

photo of force 4 at sea

Small waves, becoming longer; numerous whitecaps. Raises dust and loose paper; small branches are moved.
Wave height: 1-2m
Knots: 11-16
MPH: 13-17

photo of force 5 at sea

Moderate waves taking longer to form; many whitecaps; some spray. Small trees in leaf begin to sway; crested wavelets form on inland waters.
Wave height: 2-3m
Knots: 17-21
MPH: 18-24

photo of force 6 at sea

Larger waves forming; whitecaps everywhere; more spray. Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty.
Wave height: 3-4m
Knots: 22-27
MPH: 25-30

photo of force 7 at sea

Sea heaps up; white foam from breaking waves begins to be blown in streaks. Whole trees in motion; inconvenience felt when walking against the wind.
Wave height: 4-5.5m
Knots: 28-33
MPH: 31-38

photo of force 8 at sea

Moderately high waves of greater length; edges of crests begin to break into spindrift; foam is blown in well-marked streaks. Breaks twigs off trees; generally impedes progress.
Wave height: 5.5-7.5m
Knots: 34-40
MPH: 39-46