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TBL 10

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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

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like

Calm, smoke rises vertically

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Light Air

Scaly ripples, no foam crests

Smoke drift indicates wind direction,

wind vanes are still

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Light Breeze

Small wavelets, crests glassy, no

breaking

Wind felt on face, leaves rustle, vanes

begin to move

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Gentle Breeze

Large wavelets, crests begin to break,

scattered whitecaps

Leaves and small twigs constantly

moving, light flags extended

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Moderate Breeze  Small waves 1

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4 ft. becoming longer,

numerous whitecaps

Dust, leaves, and loose paper lifted,

small tree branches move

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Fresh Breeze

Moderate waves 4

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8 ft. taking longer

form, many whitecaps, some spray

Small trees in leaf begin to sway

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Strong Breeze

Larger waves 8

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13 ft., whitecaps

common, more spray

Larger tree branches moving, whistling

in wires

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Near Gale

Sea heaps up, waves 13

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20 ft., white

foam streaks off breakers

Whole trees moving, resistance felt

walking against wind

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Gale

Moderately high (13

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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

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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

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Storm

Very high waves (20

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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"

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Violent Storm

Exceptionally high (30

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45 ft.) waves,

foam patches cover sea, visibility more

reduced

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

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East, estimated speed 15 knots. Wind shifted from North

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East about fifteen minutes ago, and is gusty.

Special Operations

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