Hurricanes are giant whirlwinds with winds of 75 mph or more

The Associated Press has an excellent animation on their Web site demonstrating hurricane intensity. It shows the typical damage caused by hurricanes at each of the five intensity categories on the Saffir-Simpson scale. In addition, you can view 150 years of historical data and maps of hurricanes that have hit the U.S. Mainland.

Hurricanes are tropical cyclones with extremely high winds that blow in a large spiral around a relatively calm center of low pressure known as the eye of the hurricane. These violent storms can bring devastating destruction in their erratic path. This circulation is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. Near the center, hurricane winds may gust to more than 200 mph. The entire storm may dominate tens of thousands of square miles.

The eye, like the spiral structure of the storm, is unique to hurricanes. Here, winds are light and skies are clear or partly cloudy. However, this calm is deceptive, as it is bordered by maximum force winds and torrential rains. Many persons have been killed or injured when the calm eye lured them out of shelter, only to be caught in the maximum winds at the far side of the eye, where the wind blows from a direction opposite of that in the leading half of the storm.

While hurricane winds do a lot damage, drowning is the greatest cause of deaths in a hurricane. As the storm approaches and moves across the coastline, it brings huge waves and storm tides which may reach 25 feet or more above normal. The rise may come rapidly, flooding coastal lowlands. Waves and currents erode beaches and barrier islands, undermine structures and wash out highway and railroad beds. The accompanying torrential rains produce sudden flooding as the storm moves inland. As its winds diminish, rainfall floods constitute the hurricane’s greatest threat.

The hurricanes that strike the eastern United States are born in the tropical and subtropical North Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico. Most occur in August, September and October; however, the six-month period from June 1 to November 20 is considered the Atlantic hurricane season.

Most Numerous:

27 named storms (previous record: 21 in 1933)
14 hurricanes (previous record: 12 in 1969)
Four major hurricanes hitting the U.S. (previous record: three in 2004)
Three Category 5 hurricanes (previous record: two in 1960 and 1961)
Seven tropical storms before August 1 (previous record: five in 1997)
Two-year consecutive total of tropical storms: 42 (previous record: 32 most recently in 1995-96)
Two-year consecutive total of hurricanes: 25 (previous record: 21 in 1886-87)
Two-year consecutive total of major hurricanes: 13 (ties record in 1950-51)
Two-year consecutive major hurricane landfalls: Seven (previous record: five in 1954-55)
Two -year consecutive Florida major hurricane landfalls: Five (previous record: three in 1949-50)
Three-year consecutive total of tropical storms: 58 (previous record: 43 most recently in 2002-04)
Three-year consecutive total of hurricanes: 31 (previous record: 27 in 1886-88)
Three-year consecutive total of major hurricanes: 16 (ties record in 1949-51 and 1950-52)

Costliest:

Hurricane: Katrina (at least $80 billion) - (previous record Andrew, $26.5 billion - 1992 dollars)

Deadliest:

U.S. hurricane since 1928: Katrina (at least 1,300)

Strongest:

* Hurricane in the Atlantic Basin: Wilma 882 millibars (mb) - (previous record: Gilbert at 888 mb)
* Three of the six strongest hurricanes on record: Wilma 882 mb (1st), Rita 897 mb (4th), Katrina 902 mb (6th)

* Source: NOAA

Categories & Wind Speed:
Hurricanes are categorized according to the strength of their winds using the Saffir-Simpson Scale. These are relative terms, because lower category storms can sometimes inflict greater damage than higher category storms.

1 Minimal (74-95 mph)......................Example: Hurricane Erin (1995)
Expect damage primarily to unanchored mobile homes, shrubbery, and trees. Also, some coastal road flooding and minor pier damage.

2 Moderate (96-110 mph)......................Example: Hurricane Frances (2004)
Expect some roofing material, door, and window damage to buildings. Considerable damage to vegetation, mobile homes, and piers. Coastal and low-lying escape routes flood 2-4 hours before arrival of center. Small craft in unprotected anchorages break moorings.

3 Extensive (111-130 mph)......................Examples: Hurricanes Ivan and Jeanne (2004)
Expect some structural damage to small residences and utility buildings with a minor amount of curtain wall failures. Mobile homes are destroyed. Flooding near the coast destroys smaller structures with larger structures damaged by floating debris. Terrain continuously lower than 5 feet above sea level (ASL), may be flooded inland 8 miles or more.

4 Extreme (131-155 mph)...........Examples: Hurricane Charley (2004); Hurricanes Dennis & Emily (2005)
Expect more extensive curtain wall failures with some complete roof structure failure on small residences. Major erosion of beach areas. Major damage to lower floors of structures near the shore. Terrain continuously lower than 10 feet ASL may be flooded requiring massive evacuation of residential areas inland as far as 6 miles.

5 Catastrophic (156 + mph)......................Examples: Hurricanes Katrina, Rita and Wilma (2005)
Expect complete roof failure on many residences and industrial buildings. Some complete building failures with small utility buildings blown over or away. Major damage to lower floors of all structures located less than 15 feet ASL and within 500 yards of the shoreline. Massive evacuation of residential areas on low ground within 5 to 10 miles of the shoreline may be required.

To report an outage by phone, call 1-800-SECO-141 (1-800-732-6141) or your local SECO office and follow the prompts. To report an outage online go to SECO's Storm Center/report.

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Page last updated: Thursday, February 28, 2008