The Beaufort Scale of wind strength


The following table describes wind speed in terms of the Beaufort scale...

Force Name Description Wind Speed Wave Height (m)
Sea Land kts mph kph m/s AVG MAX
0 Calm Sea like a mirror Tree leaves don't move; smoke rises vertically 0

1

0

1

0

1

0

0.2

0 0
1 Light air Ripples with appearance of scales, no crests form Tree leaves don't move; smoke drifts slowly 1

3

1

3

1

5

0.3

1.5

0.1 0.1
2 Light breeze Wavelets, small but pronounced. Crests with glassy appearance, but do not break Tree leaves rustle; flags wave slightly 4

6

4

7

6

11

1.6

3.3

0.2 0.3
3 Gentle breeze Large wavelets, crests begin to break. Glassy looking foam, occasional white horses Leaves and twigs in constant motion; small flags extended 7

10

8

11

12

19

3.4

5.4

0.6 1.0
4 Moderate breeze Small waves becoming longer, frequent white horses Small branches move; flags flap 11

16

13

18

20

29

5.5

7.9

1.0 1.5
5 Fresh breeze Moderate waves of pronounced long form. Many white horses, some spray Small trees sway; flags flap and ripple 17

21

19

24

30

38

8.0

10.7

2.0 2.5
6 Strong breeze Some large waves, extensive white foam crests, some spray Large branches sway; flags beat and pop 22

27

25

31

39

50

10.8

13.8

3.0 4.0
7 Near gale Sea heaped up, white foam from breaking waves blowing in streaks with the wind Whole trees sway 28

33

32

38

51

61

13.9

17.1

4.0 5.5
8 Gale Moderately high and long waves. Crests break into spin drift, blowing foam in well marked streaks Twigs break off trees 34

40

39

46

62

74

17.2

20.7

6.0 7.5
9 Severe gale High waves, dense foam streaks in wind, wave crests topple, tumble and roll over. Spray reduces visibility Branches break off trees; tiles blown from roofs 41

47

47

54

75

86

20.8

24.4

7.0 10.0
10 Storm Very high waves with long overhanging crests. Dense blowing foam, sea surface appears white. Heavy tumbling of sea, shock-like, poor visibility Some trees blown down; damage to buildings 48

55

55

63

87

101

24.5

28.4

9.0 12.5
11 Severe storm Exceptionally high waves, sometimes concealing small and medium sized ships. Sea completely covered with long white patches of foam. Edges of wave crests blown into froth. Poor visibility Widespread damage to trees and buildings 56

63

64

74

102

120

28.5

32.6

11.5 16.0
12 Hurricane Air filled with foam and spray, sea white with driving spray, visibility poor Severe and extensive damage >63 >74 >120 >32.6 >11.5 >16.0

The Saffir-Simpson Hurricane Scale


The following table describes wind speed in terms of the Saffir-Simpson hurricane scale...

Category Name Description Wind Speed Storm Surge
Coastal Inland kts mph kph m/s ft m
1 Minimal Hurricane Low-lying coastal roads inundated, minor pier damage, some small craft in exposed anchorage torn from moorings No real damage to building structures. Damage primarily to unanchored mobile homes, shrubbery, and trees. Some damage to poorly constructed signs 64

82

75

95

121

153

33

42

4

5

1.2

1.5

2 Moderate Hurricane Coast roads and low-lying escape routes inland cut by rising water 2 to 4 hours before arrival of hurricane center. Considerable damage to piers. Marinas flooded. Small craft in unprotected anchorages torn from moorings. Evacuation of some shoreline residences and low-lying areas required Some roofing material, door, and window damage of buildings. Considerable damage to shrubbery and trees with some trees blown down. Considerable damage to mobile homes, poorly constructed signs, and piers 83

95

96

110

154

177

43

49

6

8

1.8

2.4

3 Extensive Hurricane Low-lying escape routes are cut by rising water 3-5 hours before arrival of the hurricane center. Flooding near the coast destroys smaller structures with larger structures damaged by battering of floating debris. Terrain continuously lower than 5 ft above mean sea level may be flooded inland 8 miles (13 km) or more. Evacuation of low-lying residences within several blocks of the shoreline may be required Some structural damage to small residences and utility buildings with a minor amount of curtainwall failures. Damage to shrubbery and trees with foliage blown off trees and large tress blown down. Mobile homes and poorly constructed signs are destroyed 96

113

111

130

178

209

50

58

9

12

2.7

3.7

4 Extreme Hurricane Low-lying escape routes may be cut by rising water 3-5 hours before arrival of the hurricane center. Major damage to lower floors of structures near the shore. Terrain lower than 10 ft above sea level may be flooded requiring massive evacuation of residential areas as far inland as 6 miles (10 km) More extensive curtainwall failures with some complete roof structure failures on small residences. Shrubs, trees, and all signs are blown down. Complete destruction of mobile homes. Extensive damage to doors and windows 114

135

131

155

210

249

59

69

13

18

4.0

5.5

5 Catastrophic Hurricane Low-lying escape routes are cut by rising water 3-5 hours before arrival of the hurricane center. Major damage to lower floors of all structures located less than 15 ft above sea level and within 500 yards of the shoreline. Massive evacuation of residential areas on low ground within 5-10 miles (8-16 km) of the shoreline may be required Complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. All shrubs, trees, and signs blown down. Complete destructon of mobile homes. Severe and extensive window and door damage >135 >155 >249 >70 >19 >5.5

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