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Windstorms
<br />Windstorms: Description
<br />A windstorm can be defined as a storm featuring violent winds. Damage from winds
<br />can begin at speeds exceeding 41 knots, or approximately 47 mph.
<br />Windstorms: Extent Scale
<br />Wind extent can be measured using the Beaufort Wind Scale Developed in 1805 by Sir Francis Beaufort,
<br />U.K. Royal Navy in Table 2.21.
<br />Risk Assessment
<br />ForceWindWMO
<br />(Knots)ClassificationOn the WaterOn Land
<br />0Less CalmSea surface smooth and mirror-likeCalm, smoke rises vertically
<br />than 1
<br />11-3Light AirScaly ripples, no foam crestsSmoke drift indicates wind
<br />direction, still wind vanes
<br />24-6Light BreezeSmall wavelets, crests glassy, no breakingWind felt on face, leaves rustle,
<br />vanes begin to move
<br />37-10Gentle BreezeLarge wavelets, crests begin to break, Leaves and small twigs
<br />scattered whitecapsconstantly moving, light flags
<br />extended
<br />411-16Moderate Small waves 1-4 ft. becoming longer, Dust, leaves, and loose paper
<br />Breezenumerous whitecapslifted, small tree branches move
<br />517-21Fresh BreezeModerate waves 4-8 ft taking longer form, Small trees in leaf begin to sway
<br />many whitecaps, some spray
<br />622-27Strong BreezeLarger waves 8-13 ft, whitecaps common,Larger tree branches moving,
<br />more spraywhistling in wires
<br />728-33Near GaleSea heaps up, waves 13-19 ft, white foam Whole trees moving, resistance
<br />streaks off breakersfelt walking against wind
<br />834-40GaleModerately high (18-25 ft) waves of Twigs breaking off trees,
<br />greater length, edges of crests begin to generally impedes progress
<br />break into spindrift, foam blown in streaks
<br />941-47Strong GaleHigh waves (23-32 ft), sea begins to roll, Slight structural damage occurs,
<br />dense streaks of foam, spray may reduce slate blows off roofs
<br />visibility
<br />1048-55StormVery high waves (29-41 ft) with Seldom experienced on land,
<br />overhanging crests, sea white with trees broken or uprooted,
<br />densely blown foam, heavy rolling, "considerable structural
<br />lowered visibilitydamage"
<br />1156-63Violent StormExceptionally high (37-52 ft) waves, foam
<br />patches cover sea, visibility more reduced
<br />1264+HurricaneAir filled with foam, waves over 45 ft,
<br />sea completely white with driving spray,
<br />visibility greatly reduced
<br />(NOAA, 2017)
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<br />Jurisdiction-specific data for location, previous occurrences, extent, probability, impact, and vulnerability
<br />are found in jurisdiction annexes.
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