Marine weather: the Beaufort scale, a must at sea

This ladder was designed by British Admiral Francis Beaufort in 1805. Thanks to these precise criteria, it makes it possible to analyse the wind at sea and above all, it is universal.

Calm The sea is like a mirror 1 Very light breeze A few fish scale wrinkles, but no scum. 2 Light breeze Short wavelets with glassy ridges that do not break 3 Small breeze Very small waves. The ridges are starting to break. Foam of vitreous aspect. Sometimes a few scattered sheep 4 Pretty breeze Small waves, many sheep 5 Good breeze Moderate waves clearly elongated, many sheep, possibly sea spray 6 Fresh wind Big waves begin to form. White scum ridges are sometimes more extensive. The spray is frequent. 7 Large costs The sea is getting bigger. The white foam that comes from the breaking waves begins to be blown in trails that orient themselves in the wind bed. 8 Gust of Wind Medium and longer blades. From the ridge begin to detach from the whirlwinds of sea spray. Scum trails oriented in the wind bed 9 Strong gale Big waves. Thick scum trails in the wind bed. The crest of the blades begins to flicker, collapse and break down into rolls. Spray can reduce visibility 10 Storm Very strong waves with long ridges in plume; the resulting foam, in large plates, is blown in dense white streaks into the wind bed; overall, the sea surface turns white; sea movement becomes heavy and abrupt; reduced visibility 11 Violent stormWaves of exceptional height (small vessels can disappear from view behind the waves); the sea is completely covered with white foam banks flying in the wind bed; everywhere the edges of the wave crests are blown forward; reduced visibility 12 Thunderclap The air is full of foam and spray; the sea is completely white with foam. Visibility very seriously affected

		m/s	Knots	Sea state for observation on board vessels (Sea Meters/ open)
		0 à 0.2
		0.3 à 1.5	1 3
		1.6 à 3.3	4 à 6
		3.4 à 5.4	7 à 10
		5.5 à 7.9	11 à 16
		8.0 à 10.7	17 à 21
		10.8 à 13.8	22 à 27
		13.9 à 17.1	28 à 33
		17.2 à 20.7	34 à 40
		20.8 à 24.4	41 à 47
		24.5 à 28.4	48 à 55
		28.5 à 32.6	56 à 63
		32.7 and more	64 and more