4/20/23 

AIM 

TBL 10

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2

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3 

Table of Common References for Estimating Wind Velocity 

Wind 

(Knots) 

Wind 

Classification 

Appearance of Wind Effects 

On the Water 

On Land 

Less than 1 

Calm 

Sea surface smooth and mirror

−

like 

Calm, smoke rises vertically 

1

−

3 

Light Air 

Scaly ripples, no foam crests 

Smoke drift indicates wind direction, 

wind vanes are still 

4

−

6 

Light Breeze 

Small wavelets, crests glassy, no 

breaking 

Wind felt on face, leaves rustle, vanes 

begin to move 

7

−

10 

Gentle Breeze 

Large wavelets, crests begin to break, 

scattered whitecaps 

Leaves and small twigs constantly 

moving, light flags extended 

11

−

16 

Moderate Breeze  Small waves 1

−

4 ft. becoming longer, 

numerous whitecaps 

Dust, leaves, and loose paper lifted, 

small tree branches move 

17

−

21 

Fresh Breeze 

Moderate waves 4

−

8 ft. taking longer 

form, many whitecaps, some spray 

Small trees in leaf begin to sway 

22

−

27 

Strong Breeze 

Larger waves 8

−

13 ft., whitecaps 

common, more spray 

Larger tree branches moving, whistling 

in wires 

28

−

33 

Near Gale 

Sea heaps up, waves 13

−

20 ft., white 

foam streaks off breakers 

Whole trees moving, resistance felt 

walking against wind 

34

−

40 

Gale 

Moderately high (13

−

20 ft.) waves of 

greater length, edges of crests begin to 

break into spindrift, foam blown in 

streaks 

Whole trees in motion, resistance felt 

walking against wind 

41

−

47 

Strong Gale 

High waves (20 ft.), sea begins to roll, 

dense streaks of foam, spray may reduce 

visibility 

Slight structural damage occurs, slate 

blows off roofs 

48

−

55 

Storm 

Very high waves (20

−

30 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” 

56

−

63 

Violent Storm 

Exceptionally high (30

−

45 ft.) waves, 

foam patches cover sea, visibility more 

reduced 

64+ 

Hurricane 

Air filled with foam, waves over 45 ft., 

sea completely white with driving spray, 

visibility greatly reduced 

EXAMPLE

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Wind from the South

−

East, estimated speed 15 knots. Wind shifted from North

−

East about fifteen minutes ago, and is gusty. 

Special Operations 

10

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2

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15