WeAther-relAteD scAles

saffir-simpson hurricane scale

•

Tropical Storm

Winds 39–73 mph

•

Category 1 Hurricane — winds 74–95 mph (64–82

knots); pressure greater than 980 mbar; storm surge 3–5 ft

(1 .0–1 .7 m)

No real damage to buildings . Damage to unanchored mo-

bile homes . Some damage to poorly constructed signs .

Also, some coastal flooding and minor pier damage .

— Examples: Irene 1999 and Allison 1995

•

Category 2 Hurricane — winds 96–110 mph (83–95 knots);

pressure 979–965 mbar; storm surge 6–8 ft (1 .8–2 .6 m)

Some damage to building roofs, doors and windows .

Considerable damage to mobile homes . Flooding dam-

ages piers and small craft in unprotected moorings

may break their moorings . Some trees blown down .

— Examples: Bonnie 1998, Georges (FL & LA) 1998 and

Gloria 1985

•

Category 3 Hurricane — winds 111–130 mph (96–113

knots); pressure 964–945 mbar; storm surge 9–12 ft (2 .7–

3 .8 m)

Some structural damage to small residences and utility build-

ings . Large trees blown down . Mobile homes and poorly

built signs destroyed . Flooding near the coast destroys

smaller structures with larger structures damaged by

floating debris . Terrain may be flooded well inland .

— Examples: Keith 2000, Fran 1996, Opal 1995, Alicia

1983 and Betsy 1965

•

Category 4 Hurricane — winds 131–155 mph (114–135

knots); pressure 944–920 mbar; storm surge 13–18 ft (3 .9–

5 .6 m)

More extensive curtainwall failures with some complete roof

structure failure on small residences . Major erosion of

beach areas . Terrain may be flooded well inland .

— Examples: Hugo 1989 and Donna 1960

•

Category 5 Hurricane — winds 156 mph and up (135+

knots); pressure less than 920 mbar; storm surge 19+ ft

(5 .7+ m)

Complete roof failure on many residences and industrial

buildings . Some complete building failures with small

utility buildings blown over or away . Flooding causes

major damage to lower floors of all structures near the

shoreline . Massive evacuation of residential areas may

be required .

— Examples: Andrew (FL) 1992, Camille 1969 and Labor

Day 1935

fujita tornado Damage scale

The original Fujita Scale was modified by NOAA in February

2007 and is now called the Enhanced Fujita Scale (EF) . It is an

operational scale based on the estimated speed of three-second

wind gusts, as indicated by typical damage levels . The table below

describes the damage levels according to the original scale . In the

enhanced scale, the damage is measured by a more elaborate set of

criteria (see http://www .spc .noaa .gov/efscale/ef-scale .html) .

beaufort Wind scale

The Beaufort Wind Scale was devised by British Rear-Admiral Sir Francis Beaufort in 1805 based on observations of the effects of the

wind .

EF

Number

3 s Gusts

(mph)

Typical damage (according to the original Fujita Scale)

0

65–85

Light damage. Some damage to chimneys; branches broken off trees; shallow-rooted trees pushed over; sign

boards damaged .

1

86–110 Moderate damage. Peels surface off roofs; mobile homes pushed off foundations or overturned; moving

autos blown off roads .

2

111–135 Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large

trees snapped or uprooted; light-object missiles generated; cars lifted off ground .

3

136–165 Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in

forest uprooted; heavy cars lifted off the ground and thrown .

4

166–200 Devastating damage. Well-constructed houses leveled; structures with weak foundations blown away some

distance; cars thrown and large missiles generated .

5

Over 200 Incredible damage. Strong frame houses leveled off foundations and swept away; automobile-sized missiles

fly through the air in excess of 100 meters (109 yd); trees debarked; incredible phenomena will occur .

Force

Wind

(knots)

WMO

classification

Appearance of wind effects

On the water

On land

0

< 1

Calm

Sea surface smooth and mirror-like

Calm, smoke rises vertically

1

1–3

Light Air

Scaly ripples, no foam crests

Smoke drift indicates wind direction, still wind vanes

2

4–6

Light Breeze

Small wavelets, crests glassy, no breaking

Wind felt on face, leaves rustle, vanes begin to move

3

7–10 Gentle Breeze

Large wavelets, crests begin to break, scattered

whitecaps

Leaves and small twigs constantly moving, light flags

extended

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Force

Wind

(knots)

WMO

classification

Appearance of wind effects

On the water

On land

4

11–16 Moderate Breeze Small waves 1–4 ft . becoming longer, numerous

whitecaps

Dust, leaves, and loose paper lifted, small tree branches

move

5

17–21 Fresh Breeze

Moderate waves 4–8 ft taking longer form, many

whitecaps, some spray

Small trees in leaf begin to sway

6

22–27 Strong Breeze

Larger waves 8–13 ft, whitecaps common, more spray

Larger tree branches moving, whistling in wires

7

28–33 Near Gale

Sea heaps up, waves 13–20 ft, white foam streaks off

breakers

Whole trees moving, resistance felt walking against

wind

8

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

9

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

10

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”

11

56–63 Violent Storm

Exceptionally high (30–45 ft) waves, foam patches

cover sea, visibility more reduced

12

64+

Hurricane

Air filled with foam, waves over 45 ft, sea completely

white with driving spray, visibility greatly reduced

Wind chill

The following chart prepared by the U . S . National Weather Service gives the temperature perceived by an average person as a func-

tion of the real air temperature and the wind speed . The current scale was adopted in 2001 .

reference

National Oceanic and Atmospheric Administration, http://www .noaa .gov

Weather-Related Scales

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