Lesson 2

The Beaufort Wind Scale

The Beaufort wind scale (0-12) is used by sailors in order to describe the effects of the wind on the water. Thus each separate number on the scale comprises a range of the wind speeds. The effects seen on water are relevant mostly at sea, but also on any other large body of water, such as the Great Lakes in North America. Effects on land are also specified. And now to the scale:

Beaufort scale	Description of wind, and its speed (in knots)	Effects seen at sea or a large lake	Effects seen on land
0	calm, less than 1	water is flat, like a mirror	smoke rises vertically
1	light air, 1-3	water is slightly rippled	smoke drifts, weather vanes are motionless
2	light breeze, 4-6	very small waves	breeze can be felt on face, weather vanes move a little, leaves rustle
3	gentle breeze, 7-10	waves larger, wave crests begin to break, occasional whitecaps possible	leaves are in motion constantly, light flags extend
4	moderate breeze, 11-16	waves 0.5-1.25 meters high (roughly 1.7 - 4.1 feet), a lot of whitecaps	small branches begin to move, loose paper and dust can be raised
5	fresh breeze, 17-21	waves 1.5-2.5 meters high (roughly 4.10 - 8.3 feet), many whitecaps, some spray	tops of all trees are in motion, small trees are swayed
6	strong breeze, 22-27	waves larger, 2.5-4 meters high (roughly 8.3 - 13.2 feet), whitecaps everywhere, more spray	large tree branches begin to move, whistling is heard through wires
7	near gale, 28-33	waves are 4-6 meters high (roughly 13.2 - 19.8 feet), white foam from the breaking waves is blown along the line of the wind direction	even large trees are in motion
8	gale, 34-40	waves still 4-6 meters high, but longer than at 7, wave crests begin to break into spin-drift, streaks of foam are seen everywhere	twigs can be broken off trees, walking is more difficult
9	strong gale, 41-47	waves are high, about 6 meters (19.8 feet), water starts to roll, visibility affected by the spray	fences can be blown down, shingles can be blown from the roofs
10	storm, 48-55	very high waves are formed, 6-9 meters (19.8 - 29.7 feet), heavily rolling water, overhanging crests, visibility strongly affected	not often experienced on land, trees will be broken or uprooted, damage in structures will be considerable
11	violent storm, 56-63	waves are extremely high, 9-14 meters (29.7 - 46 feet), water has a white appearance from foam patches	not experienced on land
12	hurricane, 64 and up	waves are over 14 meters high (over 46 feet), air is filled with foam, water has a white appearance, visibility greatly reduced	not experienced on land

Lesson 3: "Points of Sail"