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Measuring the wind

In 1805, a British Naval officer called Francis Beaufort introduced a scale from 0 -12 for measuring the speed of the wind at sea. Admiral Beaufort developed the scale based on his observations of the wind and waves and used everyday terms for each level of his scale.

Light air

The Beaufort Scale is still used today to describe the speed of wind at sea and the effect of wind on the surface of the water. Wind speed is measured in knots, with one knot equal to one nautical mile per hour. A nautical mile is just a bit longer than a land mile.

Today we also use wind instruments to measure the exact speed of the wind.

So lets’ take a look at the Beaufort Scale – the force, the speed of the wind in knots, how you would describe the wind and how you would describe the state of the sea...

Force Knots Description Sea Description
0 1 knot Calm Calm (glassy)
1 1 – 3 knots Light air Calm (rippled)
4 – 6 knots
Light breeze
Smooth (wavelets)
7 – 10 knots
Gentle breeze
11 – 16 knots
Moderate breeze
Slight – Moderate
17 – 21 knots
Fresh breeze
22 – 27 knots
Strong breeze
28 – 33 knots
Near gale
Rough – Very Rough
34 – 40 knots
Very rough – High
41 – 47 knots
Severe gale
48 – 55 knots
Very High
56 – 63 knots
Violent storm
Very High
Over 64 knots

Next time you’re out on the water why not practise working out what force you think the wind is and then check on the boat’s instruments to see if you’re right!

Rough weather

As well as knowing how strong the wind is, when you’re out on the water you’ll need to learn where the wind is coming from, this is called wind direction.

The wind direction is shown by which point of the compass the wind is blowing from. For example a south wind blows from the south, NOT to the south!

Wind direction

Brainteaser – when is a knot, not a knot?

When it’s a nautical mile per hour!

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