Scala Beaufort, vânt.

Wind Force	Description	Wind Speed			Specifications	Probable Wave Height		Sea State
		km/h	mph	knots		metres	Max
0	Calm	<1	<1	<1	Smoke rises vertically. Sea like a mirror	--	--	0
1	Light Air	1-5	1-3	1-3	Direction shown by smoke drift but not by wind vanes. Sea rippled	0.1	0.1	1
2	Light Breeze	6-11	4-7	4-6	Wind felt on face; leaves rustle; wind vane moved by wind. Small wavelets on sea	0.2	0.3	2
3	Gentle Breeze	12-19	8-12	7-10	Leaves and small twigs in constant motion; light flags extended. Large wavelets on sea	0.6	1.0	3
4	Moderate Breeze	20-28	13-18	11-16	Raises dust and lose paper; small branches moved. Small waves, fairly frequent white horses	1.0	1.5	3-4
5	Fresh Breeze	29-38	19-24	17-21	Small trees in leaf begin to sway; crested wavelets form on inland waters. Moderate waves, many white horses	2.0	2.5	4
6	Strong Breeze	38-49	25-31	22-27	Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty. Large waves, extensive foam crests	3.0	4	5
7	Near Gale	50-61	32-38	28-33	Whole trees in motion; inconvenience felt when walking against the wind. Foam blown in streaks across the sea	4.0	5.5	5-6
8	Gale	62-74	39-46	34-40	Twigs break off trees; generally impedes progress. Wave crests begin to break into spindrift	5.5	7.5	6-7
9	Strong Gale	75-88	47-54	41-47	Slight structural damage (chimney pots and slates removed). Wave crests topple over, and spray affects visibility	7.0	10.0	7
10	Storm	89-102	55-63	48-55	Seldom experienced inland; trees uprooted; considerable structural damage. Sea surface is largely white	9.0	12.5	8
11	Violent Storm	103-117	64-72	56-63	Very rarely experienced, accompanied by widespread damage. Medium-sized ships lost to view behind waves. Sea covered in white foam, visibility seriously affected	11.5	16.0	8
12	Hurricane	118+	73+	64+	Devastation. Air filled with foam and spray, very poor visibility	14+	---	9

 

About Sir Francis Beaufort

The scale was devised in 1805 by the Irish hydrographer Francis Beaufort (later Rear Admiral Sir Francis Beaufort), a Royal Navy officer while serving on HMS Woolwich. The scale that carries Beaufort's name had a long and complex evolution from the previous work of others (including Daniel Defoe the century before) to when Beaufort was Hydrographer of the Navy in the 1830s when it was adopted officially and first used during the voyage of HMS Beagle under Captain Robert FitzRoy, later to set up the first Meteorological Office (Met Office) in Britain giving regular weather forecasts.

In the early 19th century, naval officers made regular weather observations, but there was no standard scale, so they could be very subjective – one man's "stiff breeze" might be another's "soft breeze". Beaufort succeeded in standardising the scale.

(From Wikipedia)