The Saffir-Simpson Hurricane Scale is a 1-5 rating based on the
hurricane's present intensity. This is used to give an estimate of the
potential property damage and flooding expected along the coast from a
hurricane landfall. Wind speed is the determining factor in the scale, as storm
surge values are highly dependent on the slope of the continental shelf in the
landfall region. Note that all winds are using the U.S. 1-minute average.
Category
One Hurricane:
Winds
74-95 mph (64-82 kt or 119-153 km/hr). 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.
Category
Two Hurricane:
Winds
96-110 mph (83-95 kt or 154-177 km/hr). 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 Bonnie of 1998
was a Category Two hurricane when it hit the North Carolina coast, while Hurricane Georges of
1998 was a Category Two Hurricane when it hit the Florida Keys and the
Mississippi Gulf Coast.
Category
Three Hurricane:
Winds
111-130 mph (96-113 kt or 178-209 km/hr). 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 trees 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 center of the hurricane. Flooding near
the coast destroys smaller structures with larger structures damaged by
battering from 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.
Category
Four Hurricane:
Winds
131-155 mph (114-135 kt or 210-249 km/hr). 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 center of the hurricane. 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.
Category
Five Hurricane:
Winds greater than 155 mph (135 kt or 249 km/hr). 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 center of the hurricane. 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. Hurricane Mitch of 1998
was a Category Five hurricane at peak intensity over the western Caribbean. Hurricane Gilbert of
1988 was a Category Five hurricane at peak intensity and is one of the
strongest Atlantic tropical cyclones of record.