The Saffir-Simpson Hurricane Scale
The scale was formulated in 1969 by Herbert Saffir, a consulting engineer, and Dr. Bob Simpson, director of the National Hurricane Center.
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 - not the International 10-minute average*.
* Since surface winds and gusts can change dramatically over short time intervals, it is necessary to define the length of time over which the winds are to be measured. For a cyclone of some given intensity, longer wind averaging times will yield lower maximum winds. Unfortunately, different meteorological services use different averaging times. Following World Meteorological Organization (WMO) guidelines, most regions use a 10-minute average. However, the Joint Typhoon Warning Center (JTWC), Guam, and WMO Region IV (United States and Caribbean area) use a 1-minute standard average. This use of a different time base results in sustained winds on foreign warnings being about 12 percent lower than those of U.S. warnings.
Storm Category ~ Barometric Pressure (Inches) ~ Winds (MPH) ~ Storm Surge (Feet)
1 ~ 28.94" ~ 74 – 95 mph ~ 4 – 5'
2 ~ 28.50 – 28.91" ~ 96 – 110 mph ~ 6 – 8'
3 ~ 27.91 – 28.47" ~ 111 – 130 mph ~ 9 – 12'
4 ~ 27.17 – 27.88" ~ 131 – 155 mph ~ 13 – 18'
5 ~ 27.17" ~ 155 mph ~ 18'+
Tropical Depression < 39 mph
Tropical Storm 39-73 mph
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
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.
became a hurricane on August 22 and strengthened to a strong category 4 hurricane the next day. As it moved westward, it weakened to 941 millibars as it passed over Great Bahama Bank on the 24th, but rapidly re-intensified as it moved over the Gulfstream on its approach to Florida
. Andrew was the third most intense U.S. land-falling (August 24, 1992) hurricane this century, and the strongest since Hurricane Camille in 1969. With a central pressure of 922 mb, and sustained wind speeds of 125 knots (about 145 mph) with gusts near 150 knots (175 mph), Andrew was a Category Four hurricane. Andrew came ashore near high tide and brought with it a 16.9 foot storm tide (the sum of the storm surge and astronomical tide) into Biscayne Bay, a record
maximum for the southeast Florida
peninsula. After striking Florida, Andrew moved northwest across the Gulf of Mexico
to make a second U.S. landfall in a sparsely populated area of south-central Louisiana as a Category 3 storm on August 26.
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