WHAT IS A HURRICANE?
The terms “hurricane” and “typhoon” are regionally specific names for a strong “tropical cyclone”. A tropical cyclone is the generic term for a non-frontal synoptic scale low-pressure system over tropical or sub-tropical waters with organized convection (i.e. thunderstorm activity) and definite cyclonic surface wind circulation (Holland 1993).
Tropical cyclones with maximum sustained surface winds of less than 17 m/s (34 kt, 39 mph) are called “tropical depressions”. Once the tropical cyclone reaches winds of at least 17 m/s (34 kt, 39 mph) they are typically called a “tropical storm” and assigned a name. If winds reach 33 m/s (64 kt, 74 mph)), then they are called:
• “HURRICANE” (North Atlantic Ocean, Northeast Pacific Ocean east of the dateline, or South Pacific Ocean east of 160E)
• “TYPHOON” (Northwest Pacific Ocean west of the dateline)
• “SEVERE TROPICAL CYCLONE” (Southwest Pacific Ocean west of 160E or Southeast Indian Ocean east of 90E)
• “SEVERE TROPICAL STORM” (North Indian Ocean)
• “TROPICAL CYCLONE” (Southwest Indian Ocean)
|10 COSTLIEST HURRICANES TO STRIKE THE US MAINLAND (1)||Estimated Insured Loss In Billions (2)|
|RANK||DATE||LOCATION||HURRICANE||DOLLARS WHEN OCCURRED||IN 2012 DOLLARS (3)|
|1||Aug. 25-30, 2005||AL, FL, GA, LA, MS, TN||Katrina||$ 41,100||$ 47,424|
|2||Aug. 24-26, 1992||FL, LA||Andrew||$ 15,500||$ 23,349|
|3||Oct. 28-31, 2012||CT, DC, DE, MA, MD, ME, NC, NH,
NJ, NY, OH, PA, RI, VA, VT, WV
|4||Sep. 12-14, 2008||AR, IL, IN, KY, LA, MO, OH, PA, TX||Ike||$ 12,500||$ 13,283|
|5||Oct. 24, 2005||FL||Wilma||$ 10,300||$ 11,885|
|6||Aug. 13-14, 2004||FL, NC, SC||Charley||$ 7,475||$ 8,912|
|7||Sep. 15-21, 2004||AL, DE, FL, GA, LA, MD, MS, NJ, NY, NC, OH, PA, TN, VA, WV||Ivan||$ 7,110||$ 8,476|
|8||Sep. 17-22, 1989||GA, NC, PR, SC, VA, U.S. Virgin Islands||Hugo||$ 4,195||$ 6,957|
|9||Sep. 20-26, 2005||AL, AR, FL, LA, MS, TN, TX||Rita||$ 5,627||$ 6,493|
|10||Sep. 3-9, 2004||FL, GA, NY, NC, SC||Frances||$ 4,595||$ 5,478|
(1) Includes hurricanes occurring through 2012. (2) Property coverage only. Does not include flood damage covered by the federally administered National Flood Insurance Program. (3) Adjusted for inflation through 2012 by ISO using the GDP implicit price deflator. Source: Insurance Information Institute.
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. one minute average speed.
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 curtain wall 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 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 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. Hurricane Andrew in 1992 was a devastating Category Five hurricane and rather than being a wet storm as are so many tropical cyclones, it acted as if it were one large 25 mile wide tornado.