Publications

Last Updated:

July 25, 2013

 
The Extended Beaufort Wind Scale

The Beaufort wind scale was devised in 1805 by British Rear-Admiral, Sir Francis Beaufort (1774–1857) and was extended in 1946.

Beaufort scale

Wind speed at 10 m

Wave height (m)

WMO classification

Appearance of wind effects

Tropical Cyclone Category

m/s

Knots

km/h

On the sea

On land

0

0.0–0.2

<1

<1

Calm

Sea surface smooth and mirror-like

Calm, smoke rises vertically

1

0.3–1.5

1–3

1–5

0.1

Light air

Scaly ripples, no foam crests

Smoke drift indicates wind direction, still wind vanes

2

1.6–3.3

4–6

6–11

0.2

Light breeze

Small wavelets, crests glassy, no breaking

Wind felt on face, leaves rustle, vanes begin to move

3

3.4–5.4

7–10

12–19

0.6

Gentle breeze

Large wavelets, crests begin to break, scattered whitecaps

Leaves and small twigs constantly moving, light flags extended

4

5.5–7.9

11–16

20–28

1.0

Moderate breeze

Small waves 1–4 ft. becoming longer, numerous whitecaps

Dust, leaves, and loose paper lifted, small tree branches move

5

8.0–10.7

17–21

29–38

2.0

Fresh breeze

Moderate waves 4–8 ft taking longer form, many whitecaps, some spray

Small trees in leaf begin to sway

6

10.8–13.8

22–27

39–49

3.0

Strong breeze

Larger waves 8–13 ft, whitecaps common, more spray

Larger tree branches moving, whistling in wires

Tropical Depression

7

13.9–17.1

28–33

50–61

4.0

Near gale

Sea heaps up, waves 13–19 ft, white foam streaks off breakers

Whole trees moving, resistance felt walking against wind

8

17.2–20.7

34–40

62–74

5.5

Gale

Moderately high (18–25 ft) waves of greater length, edges of crests begin to break into spindrift, foam blown in streaks

Twigs breaking off trees, generally impedes progress

Tropical Storm

9

20.8–24.4

41–47

75–88

7.0

Strong gale

High waves (23–32 ft), sea begins to roll, dense streaks of foam, spray may reduce visibility

Slight structural damage occurs, slate blows off roofs

10

24.5–28.4

48–55

89–102

9.0

Storm

Very high waves (29–41 ft) with overhanging crests, sea white with densely blown foam, heavy rolling, lowered visibility

Seldom experienced on land, trees broken or uprooted, ‘considerable structural damage’

Severe Tropical Storm

11

28.5–32.6

56–63

103–117

11.5

Violent storm

Exceptionally high (37–52 ft) waves, foam patches cover sea, visibility more reduced

 

12

32.7–36.9

64–71

118–133

14.0

Hurricane

Air filled with foam, waves over 45 ft, sea completely white with driving spray, visibility greatly reduced

 

Typhoon

13

37.0–41.4

72–80

134–149

 

 

 

 

14

41.5–46.1

81–89

150–166

 

 

 

 

Severe Typhoon

15

46.2–50.9

90–99

167–183

 

 

 

 

16

51.0–56.0

100–108

184–201

 

 

 

 

Super Typhoon

17

56.1–61.2

109–118

202–220

 

 

 

 

 

61.3–

119–

221–