Appearance of Wind Effects
Force Wind
(Knots) WMO
Classification
On the Water On Land
0 Less than 1 Calm Sea surface smooth and mirror-like Calm, smoke rises vertically
1 1-3 Light Air Scaly ripples, no foam crests Smoke drift indicates wind direction, still wind vanes
2 4-6 Light Breeze Small wavelets, crests glassy, Wind felt on face, leaves no breaking rustle, vanes begin to move
3 7-10 Gentle Breeze Large wavelets, crests begin to break, Leaves and small twigs
scattered whitecaps constantly moving, light flags extended
4 11-16 Moderate Breeze S mall waves 1-4 ft. Dust, leaves, and loose paper
numerous whitecaps becoming longer lifted, small tree branches move
5 17-21 Fresh Breeze Moderate waves 4-8 ft Small trees in leaf begin to sway
taking longer form, many whitecaps,
some spray
6 22-27 Strong Breeze Larger waves 8-13 ft, Larger tree branches moving
whitecaps common, more spray whistling in wires
7 28-33 Near Gale Sea heaps up, waves 13-19 ft, Whole trees moving
white foam streaks off breakers resistance felt walking against wind
8 34-40 Gale Moderately high (18-25 ft) waves Twigs breaking off trees
of greater length, edges of crests generally impedes progress
begin to break into spindrift,
foam blown in streaks
9 41-47 Strong Gale High waves (23-32 ft), Slight structural damage occurs,
sea begins to roll, slate blows off roofs
dense streaks of foam,
spray may reduce visibility
10 48-55 Storm Very high waves (29-41 ft) Seldom experienced on land,
with overhanging crests, trees broken or uprooted,
sea white with densely blown foam, "considerable structural damage"
heavy rolling, lowered visibility
11 56-63 Violent Storm Exceptionally high
(37-52 ft) waves, foam patches cover sea,
visibility more reduced
12 64+ Hurricane Air filled with foam, waves over 45 ft,
sea completely white with driving spray,
visibility greatly reduced
Beaufort Wind Scale Mobile Aeronautics Education Laboratory Weather Workstation The Beaufort Scale or Beaufort Wind Force Scale is a system for estimating wind strengths without the use of instruments, based on the effects wind has on the physical environment. The behavior of smoke, waves, trees, etc., is rated on a 13 point scale of 0 (calm) to 12 (hurricane). The scale was devised in 1805 by the British naval commander, later admiral, Sir Francis Beaufort (1774-1875). A further set of numbers (13-17) for very strong winds was added by the US Weather Bureau in 1955. The Beaufort Scale, as originally drawn up, made no reference to the speed of the wind and various attempts have been made to correlate the two.
The scale is not often used today as more direct methods are used by meteorologists to measure wind speed. However, it is still useful in estimating wind speeds, especially when anemometers are not available.
Beaufort number 0 – Calm
Wind speeds: less than 1 knot (<1 kph="" mph="" mps="" p="">At sea: Sea like a mirror, calm
Sea disturbance number: 0
Probable wave height: flat (0 ft; 0 m)
On land: Smoke rises vertically
Notes: Boring, boring, boring...
Beaufort number 1 – Light Air
Wind speeds: 1-3 knots (1-3 mph; 1-5 kph; 0.3-1.5 mps)
At sea: Ripples with the appearance of scales are formed but without foam crests
Sea disturbance number: 0
Probable wave height: 5-10 cm (2-4 in) (0 ft; 0 m)
On land: Direction of wind shown by smoke drift, but not by vanes
Notes: Yachts just have steerage way
Beaufort number 2 – Light Breeze
Wind speeds: 4-6 knots (4-7 mph; 6-11 kph; 1.6-3.3 mps)
At sea: Small wavelets, still short but more pronounced;
crests have a glassy appearance and do not break
Sea disturbance number: 1
Probable wave height: 10-15 cm (4-6 in); (0-1 ft; 0-0.3 m)
On land: Wind felt on face; leaves rustle; ordinary vane moved by wind
Notes: Wind fills sails of yacht, which then may move at 1-2 knots
Beaufort number 3 – Gentle Breeze
Wind speeds: 7-10 knots (8-12 mph; 12-19 kph; 3.4-5.4 mps)
At sea: Large wavelets; crests begin to break; foam of glassy appearance; perhaps scattered white horses
Sea disturbance number: 2
Probable wave height: 60 cm (2 ft); (1-2 ft; 0.3-0.6 m)
On land: Leaves and small twigs in constant motion; wind extends light flag
Notes: Yachts start to careen and travel at 3-4 knots
Beaufort number 4 – Moderate Breeze
Wind speeds: 11-16 knots (13-18 mph; 20-28 kph; 5.5-7.9 mps)
At sea: Small waves, becoming longer; fairly frequent white crests
Sea disturbance number: 3
Probable wave height: 1 m (3.5 ft); (2-4 ft; 0.6-1.2 m)
On land: Raises dust and loose paper; small branches are moved
Notes: Good working breeze for yachts; carry all sail with good list
Beaufort number 5 – Fresh Breeze
Wind speeds: 17-21 knots (19-24 mph; 29-38 kph; 8.0-10.7 mps)
At sea: Moderate waves taking a more pronounced long form;
many white caps are formed; chance of some spray
Sea disturbance number: 4
Probable wave height: 2 m (6-7 ft); (4-8 ft; 1.2-2.4 m)
On land: Small trees in leaf begin to sway; crested wavelets form on inland waters
Notes: Yachts shorten sail
Beaufort number 6 – Strong Breeze
Wind speeds: 22-27 knots (25-31 mph; 39-49 kph; 10.8-13.8 mps)
At sea: Large waves begin to form; the white foam crests are more extensive everywhere;
probably some spray
Sea disturbance number: 5
Probable wave height: 3 m (9-10 ft); (8-13 ft; 2.4-4 m)
On land: Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty
Notes: Yachts with double reef in mainsail; care required when fishing
Beaufort number 7 – Near Gale / Moderate Gale
Wind speeds: 28-33 knots (32-38 mph; 50-61 kph; 13.9-17.1 mps)
At sea: Sea heaps up and white foam from the breaking waves begins to be blown in streaks
along the direction of the wind
Sea disturbance number: 6
Probable wave height: 4 m (13-14 ft); (13-20 ft; 4-6 m)
On land: Whole trees in motion; inconvenience felt when walking against wind
Notes: Yachts remain in harbor, those at sea “lie to”
Beaufort number 8 – Gale / Fresh Gale
Wind speeds: 34-40 knots (39-46 mph; 62-74 kph; 17.2-20.7 mps)
At sea: Moderately high waves of greater length; edges crests begin to break into spindrift;
the foam is blown in well-marked streaks along the direction of the wind
Sea disturbance number: 6
Probable wave height: 5.5 m (18 ft); (13-20 ft; 4-6 m)
On land: Breaks twigs off trees; generally impedes progress
Notes: All yachts make for harbor if possible
Beaufort number 9 – Strong Gale
Wind speeds: 41-47 knots (47-54 mph; 75-88 kph; 20.8-24.4 mps)
At sea: High waves; dense streaks of foam along the direction of wind;
crests of waves begin to topple, tumble and roll over; spray may affect visibility
Sea disturbance number: 6
Probable wave height: 7 m (23 ft); (13-20 ft; 4-6 m)
On land: Slight structural damage occurs (chimney post and slates removed)
Beaufort number 10 – Storm / Whole Gale
Wind speeds: 48-55 knots (55-63 mph; 89-102 kph; 24.5-28.4 mps)
At sea: Very high waves with long overhanging crests; resulting foam in great patches is blown in dense
white streaks along the direction of the wind; on the whole, the surface of the sea takes a white
appearance; tumbling of the sea becomes heavy and shock-like; visibility affected
Sea disturbance number: 7
Probable wave height: 9 m (29 ft); (20-30 ft; 6-9 m)
On land: Seldom experienced inland; trees uprooted; considerable structural damage occurs
Beaufort number 11 – Violent Storm / Storm
Wind speeds: 56-63 knots (64-75 mph; 103-117 kph; 28.5-32.6 mps)
At sea: Exceptionally high waves (small and medium size ships might be for a time lost from view
behind waves); sea is completely covered with long white patches of foam lying along
the direction of wind; everywhere the edges are blown into froth; visibility affected
Sea disturbance number: 8
Probable wave height: 11 m (37 ft); (30-45 ft; 9-14 m)
On land: Very rarely experienced; accompanied by widespread damage
Beaufort number 12 (-17) – Hurricane
Wind speeds: 64 knots and greater (> 75 mph; >117 kph; >32.7 mps)
At sea: The air is filled with foam and spray; sea completely white with driving spray;
visibility very seriously affected
Sea disturbance number: 9
Probable wave height: 11 m and more (> 37 ft); (>45 ft; >14 m)
On land: Very rarely experienced; accompanied by widespread damage
http://www.anbg.gov.au/jrc/kayak/beaufort.html
Force Wind
(Knots) WMO
Classification
On the Water On Land
0 Less than 1 Calm Sea surface smooth and mirror-like Calm, smoke rises vertically
1 1-3 Light Air Scaly ripples, no foam crests Smoke drift indicates wind direction, still wind vanes
2 4-6 Light Breeze Small wavelets, crests glassy, Wind felt on face, leaves no breaking rustle, vanes begin to move
3 7-10 Gentle Breeze Large wavelets, crests begin to break, Leaves and small twigs
scattered whitecaps constantly moving, light flags extended
4 11-16 Moderate Breeze S mall waves 1-4 ft. Dust, leaves, and loose paper
numerous whitecaps becoming longer lifted, small tree branches move
5 17-21 Fresh Breeze Moderate waves 4-8 ft Small trees in leaf begin to sway
taking longer form, many whitecaps,
some spray
6 22-27 Strong Breeze Larger waves 8-13 ft, Larger tree branches moving
whitecaps common, more spray whistling in wires
7 28-33 Near Gale Sea heaps up, waves 13-19 ft, Whole trees moving
white foam streaks off breakers resistance felt walking against wind
8 34-40 Gale Moderately high (18-25 ft) waves Twigs breaking off trees
of greater length, edges of crests generally impedes progress
begin to break into spindrift,
foam blown in streaks
9 41-47 Strong Gale High waves (23-32 ft), Slight structural damage occurs,
sea begins to roll, slate blows off roofs
dense streaks of foam,
spray may reduce visibility
10 48-55 Storm Very high waves (29-41 ft) Seldom experienced on land,
with overhanging crests, trees broken or uprooted,
sea white with densely blown foam, "considerable structural damage"
heavy rolling, lowered visibility
11 56-63 Violent Storm Exceptionally high
(37-52 ft) waves, foam patches cover sea,
visibility more reduced
12 64+ Hurricane Air filled with foam, waves over 45 ft,
sea completely white with driving spray,
visibility greatly reduced
Beaufort Wind Scale Mobile Aeronautics Education Laboratory Weather Workstation The Beaufort Scale or Beaufort Wind Force Scale is a system for estimating wind strengths without the use of instruments, based on the effects wind has on the physical environment. The behavior of smoke, waves, trees, etc., is rated on a 13 point scale of 0 (calm) to 12 (hurricane). The scale was devised in 1805 by the British naval commander, later admiral, Sir Francis Beaufort (1774-1875). A further set of numbers (13-17) for very strong winds was added by the US Weather Bureau in 1955. The Beaufort Scale, as originally drawn up, made no reference to the speed of the wind and various attempts have been made to correlate the two.
The scale is not often used today as more direct methods are used by meteorologists to measure wind speed. However, it is still useful in estimating wind speeds, especially when anemometers are not available.
Beaufort number 0 – Calm
Wind speeds: less than 1 knot (<1 kph="" mph="" mps="" p="">At sea: Sea like a mirror, calm
Sea disturbance number: 0
Probable wave height: flat (0 ft; 0 m)
On land: Smoke rises vertically
Notes: Boring, boring, boring...
Beaufort number 1 – Light Air
Wind speeds: 1-3 knots (1-3 mph; 1-5 kph; 0.3-1.5 mps)
At sea: Ripples with the appearance of scales are formed but without foam crests
Sea disturbance number: 0
Probable wave height: 5-10 cm (2-4 in) (0 ft; 0 m)
On land: Direction of wind shown by smoke drift, but not by vanes
Notes: Yachts just have steerage way
Beaufort number 2 – Light Breeze
Wind speeds: 4-6 knots (4-7 mph; 6-11 kph; 1.6-3.3 mps)
At sea: Small wavelets, still short but more pronounced;
crests have a glassy appearance and do not break
Sea disturbance number: 1
Probable wave height: 10-15 cm (4-6 in); (0-1 ft; 0-0.3 m)
On land: Wind felt on face; leaves rustle; ordinary vane moved by wind
Notes: Wind fills sails of yacht, which then may move at 1-2 knots
Beaufort number 3 – Gentle Breeze
Wind speeds: 7-10 knots (8-12 mph; 12-19 kph; 3.4-5.4 mps)
At sea: Large wavelets; crests begin to break; foam of glassy appearance; perhaps scattered white horses
Sea disturbance number: 2
Probable wave height: 60 cm (2 ft); (1-2 ft; 0.3-0.6 m)
On land: Leaves and small twigs in constant motion; wind extends light flag
Notes: Yachts start to careen and travel at 3-4 knots
Beaufort number 4 – Moderate Breeze
Wind speeds: 11-16 knots (13-18 mph; 20-28 kph; 5.5-7.9 mps)
At sea: Small waves, becoming longer; fairly frequent white crests
Sea disturbance number: 3
Probable wave height: 1 m (3.5 ft); (2-4 ft; 0.6-1.2 m)
On land: Raises dust and loose paper; small branches are moved
Notes: Good working breeze for yachts; carry all sail with good list
Beaufort number 5 – Fresh Breeze
Wind speeds: 17-21 knots (19-24 mph; 29-38 kph; 8.0-10.7 mps)
At sea: Moderate waves taking a more pronounced long form;
many white caps are formed; chance of some spray
Sea disturbance number: 4
Probable wave height: 2 m (6-7 ft); (4-8 ft; 1.2-2.4 m)
On land: Small trees in leaf begin to sway; crested wavelets form on inland waters
Notes: Yachts shorten sail
Beaufort number 6 – Strong Breeze
Wind speeds: 22-27 knots (25-31 mph; 39-49 kph; 10.8-13.8 mps)
At sea: Large waves begin to form; the white foam crests are more extensive everywhere;
probably some spray
Sea disturbance number: 5
Probable wave height: 3 m (9-10 ft); (8-13 ft; 2.4-4 m)
On land: Large branches in motion; whistling heard in telegraph wires; umbrellas used with difficulty
Notes: Yachts with double reef in mainsail; care required when fishing
Beaufort number 7 – Near Gale / Moderate Gale
Wind speeds: 28-33 knots (32-38 mph; 50-61 kph; 13.9-17.1 mps)
At sea: Sea heaps up and white foam from the breaking waves begins to be blown in streaks
along the direction of the wind
Sea disturbance number: 6
Probable wave height: 4 m (13-14 ft); (13-20 ft; 4-6 m)
On land: Whole trees in motion; inconvenience felt when walking against wind
Notes: Yachts remain in harbor, those at sea “lie to”
Beaufort number 8 – Gale / Fresh Gale
Wind speeds: 34-40 knots (39-46 mph; 62-74 kph; 17.2-20.7 mps)
At sea: Moderately high waves of greater length; edges crests begin to break into spindrift;
the foam is blown in well-marked streaks along the direction of the wind
Sea disturbance number: 6
Probable wave height: 5.5 m (18 ft); (13-20 ft; 4-6 m)
On land: Breaks twigs off trees; generally impedes progress
Notes: All yachts make for harbor if possible
Beaufort number 9 – Strong Gale
Wind speeds: 41-47 knots (47-54 mph; 75-88 kph; 20.8-24.4 mps)
At sea: High waves; dense streaks of foam along the direction of wind;
crests of waves begin to topple, tumble and roll over; spray may affect visibility
Sea disturbance number: 6
Probable wave height: 7 m (23 ft); (13-20 ft; 4-6 m)
On land: Slight structural damage occurs (chimney post and slates removed)
Beaufort number 10 – Storm / Whole Gale
Wind speeds: 48-55 knots (55-63 mph; 89-102 kph; 24.5-28.4 mps)
At sea: Very high waves with long overhanging crests; resulting foam in great patches is blown in dense
white streaks along the direction of the wind; on the whole, the surface of the sea takes a white
appearance; tumbling of the sea becomes heavy and shock-like; visibility affected
Sea disturbance number: 7
Probable wave height: 9 m (29 ft); (20-30 ft; 6-9 m)
On land: Seldom experienced inland; trees uprooted; considerable structural damage occurs
Beaufort number 11 – Violent Storm / Storm
Wind speeds: 56-63 knots (64-75 mph; 103-117 kph; 28.5-32.6 mps)
At sea: Exceptionally high waves (small and medium size ships might be for a time lost from view
behind waves); sea is completely covered with long white patches of foam lying along
the direction of wind; everywhere the edges are blown into froth; visibility affected
Sea disturbance number: 8
Probable wave height: 11 m (37 ft); (30-45 ft; 9-14 m)
On land: Very rarely experienced; accompanied by widespread damage
Beaufort number 12 (-17) – Hurricane
Wind speeds: 64 knots and greater (> 75 mph; >117 kph; >32.7 mps)
At sea: The air is filled with foam and spray; sea completely white with driving spray;
visibility very seriously affected
Sea disturbance number: 9
Probable wave height: 11 m and more (> 37 ft); (>45 ft; >14 m)
On land: Very rarely experienced; accompanied by widespread damage
http://www.anbg.gov.au/jrc/kayak/beaufort.html
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