AIM

4/3/14

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.