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
FujitaTornado 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
