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AIM

10/12/17

10

−2−13

Special Operations

TBL 10

−2−3

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

Wind from the South

−East, estimated speed 15 knots. Wind shifted from North−East about fifteen minutes ago, and is gusty.