Hurricane Scale, Definitions, and Other Interesting Facts

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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 1: Winds 74-95 mph. 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.

Category 1 Hurricanes of the past

- Hurricane Allison of 1995. Landfall made in Northern Florida.

- Hurricane Danny of 1997. Landfall made in Gulf Coast of Alabama.

Category 2: Winds 96-110 mph. 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.  

Category 2 Hurricanes of the past

- Hurricane Bonnie of 1998. Landfall made in North Carolina.

- Hurricane Georges of 1998. Landfall made in the Florida Keys and Mississippi Gulf Coast.

Category 3: Winds 111-130 mph. 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 or more. Evacuation of low-lying residences with several blocks of the shoreline may be required.

Category 3 Hurricanes of the past

- Hurricane Roxanne of 1995. Landfall made in the Yucatan Peninsula of Mexico

- Hurricane Fran of 1996. Landfall made in North Carolina.

Category 4: Winds 131-155 mph. Storm surge generally 13-18 ft above normal. More extensive curtain wall 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.

Category 4 Hurricanes of the past

- Hurricane Andrew of 1992. Landfall made in the South Florida.

- Hurricane Hugo of 1989. Reached Category Four status at peak intensity.

Category 5: Winds greater than 155 mph. 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.

Category 5 "Monsters": There have been only 22 Category 5 Atlantic hurricanes since record keeping began in 1886. Here is a list of these storms. Contrary to previous reports, Hurricane Andrew never was classified as a Category 5 storm even though it was the costliest in US history with over 100 direct and indirect deaths and over $26 billion dollars attributed to this storm.

Hurricane Related Definitions:

Tropical disturbance, tropical wave A cluster of clouds and thunderstorms in the tropics without a defined circulation.

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Tropical depression A rotating system of thunderstorms in the tropics with winds of less than 39mph.

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Tropical storm A rotating system of strong thunderstorms with top sustained winds of 39 to 73 mph. Storms are named when they reach this strength.

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Hurricane An intense, rotating tropical weather system with sustained winds of 74 mph or higher.

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Tropical storm watch Tropical storm conditions are possible in the watch area within about 36 hours.

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Tropical storm warning Tropical storm conditions are expected in the warning area within about 24 hours.

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Hurricane watch Hurricane conditions are possible in the watch area within about 36 hours. Your hurricane preparations should be underway.

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Hurricane warning Hurricane conditions are expected in the warning area within 24 hours. All preparations should be complete, and if evacuating, you should be on your way to a safe place.

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Storm surge A mound of ocean water up to 20 feet high that can come ashore with a hurricane. Evacuation zones are identified by the likelihood of being flooded by this rising water. Most hurricane-related deaths are from storm surge flooding. Storm surge flooding can occur over 100 miles of coastline and may extend inland several miles.