The ingredients for a hurricane include a pre-existing weather
disturbance, warm tropical oceans, moisture, and relatively
light winds aloft. If the right conditions persist long enough,
they can combine to produce the violent winds, incredible waves,
torrential rains, and floods we associate with this phenomenon.
Each year, an average of eleven tropical storms develop over the
Atlantic Ocean, Caribbean Sea, and Gulf of
Mexico. Many of these remain over the ocean and
never impact the U.S. coastline. Six of these storms
become hurricanes each year. In an average 3-year period,
roughly five hurricanes strike the
coastline, killing approximately 50 to 100 people anywhere from Texas to Maine.
Of these, two are typically "major" or "intense"
hurricanes (a category 3 or higher storm on the
Saffir-Simpson Hurricane Scale).
What is a Hurricane?
A hurricane is a type of tropical cyclone, which is a generic
term for a low pressure system that generally forms in the
tropics. The cyclone is accompanied by thunderstorms and, in the
Northern Hemisphere, a counterclockwise circulation of winds
near the earth's surface. Tropical cyclones are classified as
An organized system of clouds and thunderstorms with a defined
surface circulation and maximum sustained winds* of 38 mph or
An organized system of strong thunderstorms with a defined
surface circulation and maximum sustained winds of 39-73 mph
An intense tropical weather system of strong thunderstorms with
a well-defined surface circulation and maximum sustained winds
of 74 mph or higher
Hurricanes are categorized according to the strength of their
winds using the Saffir-Simpson Hurricane Scale. A Category 1
storm has the lowest wind speeds, while a Category 5 hurricane
has the strongest. These are relative terms, because lower
category storms can sometimes inflict greater damage than higher
category storms, depending on where they strike and the
particular hazards they bring. In fact, tropical storms can
also produce significant damage and loss of life, mainly due to
Saffir-Simpson Hurricane Scale
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.
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.
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 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.
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
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.