Hurricane Season Fast Facts

Hurricane Season Fast Facts
CNN
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Saturday, June 1, 2013 - 2:09pm

Here's a look at what you need to know about the Atlantic hurricane season, which runs from June 1 to November 30.

Facts: The National Weather Service defines a hurricane as "an intense tropical weather system with well-defined circulation and sustained winds of 74mph (64 knots) or higher."

The peak of the season is from mid-August to late October.

In the Western Northern Pacific, hurricanes are called typhoons.

Similar storms in the Indian Ocean are called cyclones.

Hurricanes are rated according to intensity on the Saffir-Simpson Hurricane Scale.

The 1-5 scale estimates potential property damage.

A Category 3 or higher is considered a major hurricane.

A hurricane watch indicates the possibility that a region could experience hurricane conditions within 48 hours.

A hurricane warning indicates that tropical-storm-force winds of at least 74 mph are expected within 36 hours.

Hurricane Development: There are three stages of development: tropical depression to tropical storm to hurricane.

Tropical depression - when a cluster of thunderstorms organizes under the right atmospheric conditions for a long enough time, with winds near the center constantly between 20 and 34 knots (23 - 39 mph).

Tropical storm - a tropical depression that has intensified to the point where its maximum sustained winds are between 35-64 knots (39-73 mph). During this time, the storm itself becomes more organized and begins to become more circular in shape -- resembling a hurricane. This is when the storm is named.

Hurricane - develops from a tropical storm as surface pressures continue to drop, and sustained wind speeds reach 64 knots (74 mph), with a pronounced rotation developing around the central core.

Hurricane Categories: From NOAA (National Oceanic and Atmospheric Administration)

The Saffir-Simpson Hurricane Scale is a 1-5 rating based on the hurricane's present intensity.

It estimates potential property damage and flooding expected along the coast from a hurricane landfall.

Wind speed is the determining factor in the scale.

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 and coastal road flooding with minor pier damage.

Category Two Hurricane Winds 96-110 mph (83-95 kt or 154-177 km/hr).

Storm surge is 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 Three Hurricane Winds 111-130 mph (96-113 kt or 178-209 km/hr).

Storm surge is 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 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 within several blocks of the shoreline may be required.

Category Four Hurricane Winds 131-155 mph (114-135 kt or 210-249 km/hr).

Storm surge is 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 off 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 flood, requiring massive evacuation of residential areas as far inland as 6 miles (10 km).

Category Five Hurricane Winds greater than 155 mph (135 kt or 249 km/hr).

Storm surge is 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 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.

Names: Once a storm system with counter-clockwise circulation and wind speeds of 39 mph or greater is identified by the Tropical Prediction Center near Miami, a name from the list is assigned to the storm

There are 11 regional lists of names, Atlantic, Eastern North Pacific, Central North Pacific, Western North Pacific, Western Australian Region, Northern Australian Region, Eastern Australian Region, Fiji Region, Papua New Guinea Region, Philippine Region and Southwest Indian Ocean.

Using women's names became the practice during World War II, following the use of a woman's name for a storm in the 1941 novel "Storm" by George R. Stewart.

In 1979, the list of hurricane names for the Atlantic regions began to include male names.

Six separate name lists are developed and agreed upon by the World Meteorological Organization.

The lists are rotated every six years.

Names associated with storms that have caused significant death and/or damage are retired from the list. Camille (1969), Andrew (1992), Opal (1995), Floyd (1999), Ivan (2004), Katrina (2005), Ike (2008) and Sandy (2012) have all been retired from the list. Once a name is removed, another name replaces it. 

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