Average number of hurricanes per month in the North Atlantic:
78% of tropical storm days, 87% of minor hurricane days and 96% of Category
3-5 hurricane days occur in August, September and October. Peak activity
in early to mid-September.
Saffir-Simpson scale for Hurricanes Sustained winds Category:
The Saffir-Simpson Hurricane Scale
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 kph).
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 kph). 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 kph). 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.
Category Four Hurricane: Winds 131-155
mph (114-135 kt or 210-249 kph). 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 Catgeory Four status at peak intensity.
Category Five Hurricane: Winds greater
than 155 mph (135 kt or 249 kph). 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 destructon 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. 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 the strongest Atlantic tropical cyclone of record.
Linear Mode
