Leaves rustle, can feel wind on your face, wind
vanes begin to move.
Small wavelets develop,
crests are glassy.
3
8-12
mph
12-19
kph
7-10
knots
Gentle Breeze
Leaves and small twigs move, light weight flags
extend.
Large wavelets, crests start to break,
some whitecaps.
4
13-18
mph
20-28
kph
11-16
knots
Moderate Breeze
Small branches move, raises dust, leaves and
paper.
Small waves develop, becoming longer,
whitecaps.
5
19-24
mph
29-38
kph
17-21
knots
Fresh Breeze
Small trees sway.
White crested wavelets (whitecaps) form, some spray.
6
25-31
mph
39-49
kph
22-27
knots
Strong Breeze
Large tree branches move, telephone wires
begin to "whistle", umbrellas are difficult to keep under control.
Larger waves form, whitecaps prevalent, spray.
7
32-38
mph
50-61
kph
28-33
knots
Moderate or Near Gale
Large trees sway, becoming difficult to walk.
Larger waves develop, white foam from breaking waves begins to be blown.
8
39-46
mph
62-74
kph
34-40
knots
Gale or Fresh Gale
Twigs and small branches are broken from trees,
walking is difficult.
Moderately large waves
with blown foam.
9
47-54
mph
75-88
kph
41-47
knots
Strong Gale
Slight damage occurs to buildings, shingles are
blown off of roofs.
High waves (6 meters),
rolling seas, dense foam, Blowing spray reduces visibility.
10
55-63
mph
89-102
kph
48-55
knots
Whole Gale or Storm
Trees are broken or uprooted, building damage
is considerable.
Large waves (6-9 meters),
overhanging crests, sea becomes white with foam, heavy rolling, reduced visibility.
11
64-72
mph
103-117
kph
56-63
knots
Violent Storm
Extensive widespread damage.
Large waves (9-14 meters), white foam, visibility further reduced.
12
73+
mph
118+
kph
64+
knots
Hurricane
Extreme destruction, devastation.
Large waves over 14 meters, air filled with foam, sea white with foam and
driving spray, little visibility.
Saffir-Simpson
Hurricane Scale
Category
Wind Strength/Pressure
Effects
1
65 to 83 knots
74 to 95 mph
119 to 153 kph
> 980 mb
Storm surge generally 4-5 ft above normal. No
real damage to building structures. Damage primarily to unanchored mobile homes,
shrubbery, and trees. Some damage to poorly constructed signs. Also, some coastal road
flooding and minor pier damage. Hurricanes Allison of 1995 and Danny of 1997 were Category
One hurricanes at peak intensity.
2
84 to 95 knots
96 to 110 mph
154 to 177 kph
980 - 965 mb
Storm surge generally 6-8 feet above normal.
Some roofing material, door, and window damage of buildings. Considerable damage to
shrubbery and trees with some trees blown down. Considerable damage to mobile homes,
poorly constructed signs, and piers. Coastal and low-lying escape routes flood 2-4 hours
before arrival of the hurricane center. Small craft in unprotected anchorages break
moorings. Hurricane Bertha of 1996 was a Category Two hurricane when it hit the North
Carolina coast, while Hurricane Marilyn of 1995 was a Category Two Hurricane when it
passed through the Virgin Islands.
3
96 to 113 knots
111 to 130 mph
178 to 209 kph
964 - 945 mb
Storm surge generally 9-12 ft above normal. Some
structural damage to small residences and utility buildings with a minor amount of
curtainwall failures. Damage to shrubbery and trees with foliage blown off trees and large
tress blown down. Mobile homes and poorly constructed signs are destroyed. Low-lying
escape routes are cut by rising water 3-5 hours before arrival of the hurricane center.
Flooding near the coast destroys smaller structures with larger structures damaged by
battering of floating debris. Terrain continuously lower than 5 ft above mean sea level
may be flooded inland 8 miles (13 km) or more. Evacuation of low-lying residences with
several blocks of the shoreline may be required. Hurricanes Roxanne of 1995 and Fran of
1996 were Category Three hurricanes at landfall on the Yucatan Peninsula of
Mexico and in
North Carolina, respectively.
4
114 to 134 knots
131 to 155 mph
210 to 249 kph
944- 920 mb
Storm surge generally 13-18 ft above normal.
More extensive curtainwall failures with some complete roof structure failures on small
residences. Shrubs, trees, and all signs are blown down. Complete destruction of mobile
homes. Extensive damage to doors and windows. Low-lying escape routes may be cut by rising
water 3-5 hours before arrival of the hurricane center. Major damage to lower floors of
structures near the shore. Terrain lower than 10 ft above sea level may be flooded
requiring massive evacuation of residential areas as far inland as 6 miles (10 km).
Hurricane Luis of 1995 was a Category Four hurricane while moving over the Leeward
Islands. Hurricanes Felix and Opal of 1995 also reached Category Four status at peak
intensity.
5
135+ knots
155+ mph
249+ kph
< 920 mb
Storm surge generally greater than 18 ft above
normal. Complete roof failure on many residences and industrial buildings. Some complete
building failures with small utility buildings blown over or away. All shrubs, trees, and
signs blown down. Complete destruction of mobile homes. Severe and extensive window and
door damage. Low-lying escape routes are cut by rising water 3-5 hours before arrival of
the hurricane center. Major damage to lower floors of all structures located less than 15
ft above sea level and within 500 yards of the shoreline. Massive evacuation of
residential areas on low ground within 5-10 miles (8-16 km) of the shoreline may be
required. There were no Category Five hurricanes in 1995, 1996, or 1997. Hurricane Gilbert
of 1988 was a Category Five hurricane at peak intensity and is the strongest Atlantic
tropical cyclone of record.
The Dvorak technique is a method using enhanced Infrared
and/or visible satellite imagery
to quantitatively estimate the intensity of a tropical system.
CI -- Current Intensity
MWS -- Mean Wind Speed
MSLP -- Mean Sea Level Atmospheric Pressure in Millibars
Forecast winds of 18 to 33 knots (21 to 38 mph).
Small Craft Advisories may also be issued for hazardous sea conditions or lower
wind speeds that may affect small craft operations.
Gale Warning
White over red lights
Forecast winds of 34 to 47 knots (39 to 54 mph)
Storm Warning
Red over red lights
Forecast winds of 48 knots (55 mph) or greater
Tropical Storm Warning
Red over red lights
Forecast winds of 48 to 63 knots (55 to 73 mph)
associated with a tropical storm
Hurricane Warning
Red over white over red
Forecast winds of 64 knots (74 mph) or higher
associated with a hurricane
Fujita Tornado
Scale
F-Scale / Intensity
Phrase
Wind Strength / Frequency
Description of Damage
F0
Gale tornado
40-72 mph
35-62 knots
64-116 kph
29%
Minimal Damage - Some damage to
chimneys, TV antennas, roof shingles and windows. Breaks branches off trees, pushes over
shallow-rooted trees, damages sign boards.
F1
Moderate tornado
73-112 mph
63-97 knots
117-180 kph
40%
Moderate Damage - Automobiles
overturned, carports destroyed, trees uprooted, peels surface off roofs, mobile homes
pushed off foundations or overturned, moving autos pushed off the roads.
F2
Significant tornado
113-157 mph
98-136 knots
181-253 kph
24%
Major Damage - Roofs torn off
frame homes, sheds and outbuildings are demolished, mobile homes overturned or destroyed,
boxcars pushed over; large trees snapped or uprooted, light object missiles
generated.
F3
Severe tornado
158-206 mph
137-179 knots
254-332 kph
6%
Severe Damage - Exterior walls
and roofs blown off well-built houses, metal buildings collapsed or are severely damaged,
trains overturned, forests and farmland flattened, heavy cars lifted off the ground and
thrown.
F4
Devastating tornado
207-260 mph
180-226 knots
333-419 kph
2%
Devastating Damage - Few walls,
if any, standing in well-built houses, structures with weak foundations blown off
some distance, large steel and concrete missiles thrown far distances, cars thrown.
F5
Incredible tornado
261-318 mph
227-276 knots
420-512 kph
less than 1%
Incredible Damage - Homes
leveled with all debris removed, strong frame houses lifted off foundations and carried
considerable distances to disintegrate. Schools, motels, and other larger structures have
considerable damage with exterior walls and roofs gone, steel re-inforced concrete
structures badly damaged. Automobile sized missiles fly through the air in excess of 100
meters, trees debarked.
F6
Inconceivable tornado
319-379 mph
277-329 knots
513-610 kph
less than 1%
These winds are very unlikely. The small area of
damage they might produce would probably not be recognizable along with the mess produced
by F4 and F5 wind that would surround the F6 winds. Missiles, such as cars and
refrigerators would do serious secondary damage that could not be directly identified as
F6 damage. If this level is ever achieved, evidence for it might only be found in some
manner of ground swirl pattern, for it may never be identifiable through engineering
studies
Weather Map Wind Symbols
1 knot = 1 nautical mile per hour = 6076 feet per
hour = 1.15078 mph
1 mph = 1 mile per hour = 5280 feet per hour = 0.86898 knots per hour
Convert from one speed to another
Type a value in one box and click here
to see the results
