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.
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Beaufort scale
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Wind speed at 10 m
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Wave height (m)
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WMO classification
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Appearance of wind effects
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Tropical Cyclone Category
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|---|---|---|---|---|---|---|---|---|
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m/s
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Knots
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km/h
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On the sea
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On land
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0
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0.0–0.2
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< 1
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< 1
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–
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Calm
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Sea surface smooth and mirror-like
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Calm, smoke rises vertically
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–
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1
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0.3–1.5
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1–3
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1–5
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0.1
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Light air
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Scaly ripples, no foam crests
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Smoke drift indicates wind direction, still wind vanes
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–
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2
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1.6–3.3
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4–6
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6–11
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0.2
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Light breeze
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Small wavelets, crests glassy, no breaking
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Wind felt on face, leaves rustle, vanes begin to move
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–
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3
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3.4–5.4
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7–10
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12–19
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0.6
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Gentle breeze
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Large wavelets, crests begin to break, scattered
whitecaps
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Leaves and small twigs constantly moving, light flags
extended
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–
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4
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5.5–7.9
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11–16
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20–28
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1
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Moderate breeze
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Small waves 1–4 ft. becoming longer, numerous
whitecaps
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Dust, leaves, and loose paper lifted, small tree
branches move
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–
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5
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8.0–10.7
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17–21
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29–38
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2
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Fresh breeze
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Moderate waves 4–8 ft taking longer form, many
whitecaps, some spray
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Small trees in leaf begin to sway
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–
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6
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10.8–13.8
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22–27
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39–49
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3
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Strong breeze
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Larger waves 8–13 ft, whitecaps common, more spray
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Larger tree branches moving, whistling in wires
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Tropical Depression
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7
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13.9–17.1
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28–33
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50–61
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4
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Near gale
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Sea heaps up, waves 13–19 ft, white foam streaks off
breakers
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Whole trees moving, resistance felt walking against
wind
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|
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8
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17.2–20.7
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34–40
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62–74
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5.5
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Gale
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Moderately high (18–25 ft) waves of greater length,
edges of crests begin to break into spindrift, foam
blown in streaks
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Twigs breaking off trees, generally impedes progress
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Tropical Storm
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9
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20.8–24.4
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41–47
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75–88
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7
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Strong gale
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High waves (23–32 ft), sea begins to roll, dense
streaks of foam, spray may reduce visibility
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Slight structural damage occurs, slate blows off roofs
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10
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24.5–28.4
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48–55
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89–102
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9
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Storm
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Very high waves (29–41 ft) with overhanging crests,
sea white with densely blown foam, heavy rolling,
lowered visibility
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Seldom experienced on land, trees broken or uprooted,
‘considerable structural damage’
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Severe Tropical Storm
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11
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28.5–32.6
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56–63
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103–117
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11.5
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Violent storm
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Exceptionally high (37–52 ft) waves, foam patches
cover sea, visibility more reduced
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||
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12
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32.7–36.9
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64–71
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118–133
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14
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Hurricane
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Air filled with foam, waves over 45 ft, sea completely
white with driving spray, visibility greatly reduced
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Typhoon
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13
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37.0–41.4
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72–80
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134–149
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14
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41.5–46.1
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81–89
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150–166
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Severe Typhoon
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15
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46.2–50.9
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90–99
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167–183
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16
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51.0–56.0
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100–108
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184–201
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Super Typhoon
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17
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56.1–61.2
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109–118
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202–220
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61.3–
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119–
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221–
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