Beaufort Scale Poster

Created in 1805 by the British admiral Francis Beaufort (1774-1857), the Beaufort scale measures the strength of the wind in 13 degrees, from force 0 (Calm) to force 12 (Hurricane). The Beaufort degree corresponds to the sea state according to the wind speed.

Where does the Beaufort scale come from?

The Beaufort scale is a measurement scale from 0 to 12 degrees that was created empirically, by comparing the average wind speed for 10 minutes.

Originally, a beaufort degree corresponds to the sea state associated with an average wind speed and the presence of foam and spray. Of course, the degrees are less accurate than measuring the wind speed with an anemometer, but at sea it is very practical to estimate the wind speed just by observing the effects of the wind on the sea surface.

It was the British admiral Francis Beaufort who invented this scale in 1805.

Why was the Beaufort scale created?

The purpose of its creation was to help the commanders of British warships to appreciate the wind and sea conditions. At the time of the Napoleonic Wars, the English had built ships in droves and recruited many officers. Young and willing to do anything to prove their worth, these officers did not reduce sail until late in the game, which frequently resulted in broken masts, torn sails or men overboard.

The Francis Beaufort scale was accompanied by a series of instructions on how to adapt the sails to wind and sea conditions.

The degrees of the Beaufort scale

The degrees of the Beaufort Scale are as follows:

Strength 0: Calm. The sea is smooth as a mirror, without waves.
Force 1: Light air The sea has a few ripples, but they don’t make foam.
Force 2: Light breeze. There are waves, but they do not break.
Force 3: Gentle breeze Small waves of less than 1m appear, and we can see some scattered white horses
Force 4: Moderate breeze The waves can reach 2m in height, and the white horses are numerous on the water.
Force 5 : Fresh breeze The tree tops shake, the waves can reach 3m.
Force 6: Strong breeze The wind whistles, the waves are crowned with a crest of foam, the waves reach 3 to 4m.
Force 7 : High wind, moderate gale, near gale The harbourmasters advise the boats not to go out. The waves can now reach 5,5m, we observe foam trails.
Force 8 : Gale, fresh gale Walking against the wind becomes almost impossible. At the crest of the waves you can see swirls of foam, the waves reach up to 7.5 m.
Force 9 : Strong/severe gale The roof tiles are flying off, the breaking waves are now reaching 10m, and the visibility is reduced by the spray.
Force 10 : Storm, whole gale Some trees are uprooted, and the surface of the sea looks white. The waves of almost 12m break in an intense and brutal way.
Force 11 : Violent storm The visibility is still reduced and the sea is completely covered with foamy banks. The 15m high waves create impressive troughs in which small ships can be lost from sight at times.
Force 12 : Hurricane The air is saturated with foam and spray; the sea is totally white, the waves are all over 15m.

How to convert the Beaufort scale to knots?

To convert the Beaufort scale to knots, the following equation can be used: Beaufort = Knots/5 + 1

1 knot = 0.514 m/s
1 knot = 1.852 Km/h