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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 and the shape
of the coastline, 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. Hurricane Lili of 2002 made landfall on the Louisiana coast as a
Category One hurricane. Hurricane Gaston of 2004 was a Category One
hurricane that made landfall along the central South Carolina coast.
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 Frances of 2004 made landfall over
the southern end of Hutchinson Island, Florida as a Category Two
hurricane. Hurricane Isabel of 2003 made landfall near Drum Inlet on the
Outer Banks of North Carolina as a Category 2 hurricane.
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 Jeanne and Ivan of 2004 were Category Three hurricanes when
they made landfall in Florida and in Alabama, 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 Charley of 2004 was a Category Four hurricane made
landfall in Charlotte County, Florida with winds of 150 mph. Hurricane
Dennis (pdf) of 2005 struck the island of Cuba as a Category Four
hurricane.
Category Five Hurricane:
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Winds greater than 155 mph (135 kt or 249 km/hr).
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Storm surge generally
greater than 18 ft above normal.
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Complete roof failure on many
residences and industrial buildings.
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Some complete building failures
with small utility buildings blown over or away.
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All shrubs, trees, and
signs blown down. Complete destruction of mobile homes.
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Severe and
extensive window and door damage.
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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. Only 3 Category Five Hurricanes
have made landfall in the United States since records began: The Labor
Day Hurricane of 1935, Hurricane Camille (1969), and Hurricane Andrew in
August, 1992. The 1935 Labor Day Hurricane struck the Florida Keys with
a minimum pressure of 892 mb--the lowest pressure ever observed in the
United States. Hurricane Camille struck the Mississippi Gulf Coast
causing a 25-foot storm surge, which inundated Pass Christian. Hurricane
Katrina (pdf), a category 5 storm over the Gulf of Mexico, was still
responsible for at least 81 billion dollars of property damage when it
struck the U.S. Gulf Coast as a category 3. It is by far the costliest
hurricane to ever strike the United States. In addition, Hurricane Wilma
(pdf) of 2005 was a Category Five hurricane at peak intensity and is the
strongest Atlantic tropical cyclone on record with a minimum pressure of
882 mb.
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