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All About
Hurricanes.....
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| A hurricane is a type of tropical cyclone (the general term for all
circulating weather systems which form over tropical waters.)
Tropical cyclones are classified as follows:
- Tropical Depression: An organized system of clouds
and thunderstorms with a defined circulation and maximum sustained winds of 38 mph (33
knots) or less.
- Tropical Storm: An organized system of strong
thunderstorms with a defined circulation and maximum sustained winds of 39 to 73 mph
(34-63 knots).
- Hurricane: An intense tropical weather system with
a well defined circulation and maximum sustained winds of 74 mph (64 knots) or higher. In
the western Pacific, hurricanes are called "typhoons," and similar storms in the
Indian Ocean are called "cyclones."
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- Hurricanes are products of the tropical ocean and
atmosphere. They are powered by heat from the sea, and they are steered by the easterly
trade winds and the temperate westerlies as well as by their own energy. Around their
core, winds grow with great velocity, generating violent seas.
- Developing hurricanes gather heat and energy through
contact with warm ocean waters. The addition of moisture by evaporation from the sea
surface powers them like giant heat engines
- Moving ashore, they sweep the ocean inward while spawning
tornadoes and producing torrential rains and floods.
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| Where and when do hurricanes usually form? |
- In the eastern Pacific, hurricanes begin forming by
mid-May
- In the Atlantic, Caribbean, and Gulf of Mexico, hurricane
development starts in June.
- For the United States, the peak hurricane threat exists
from mid-August to late October although the official hurricane season extends through
November.
- Over other parts of the world, such as the western
Pacific, hurricanes can occur year-round.
- Each year on average, ten tropical storms (of which six
become hurricanes) develop over the Atlantic Ocean, Caribbean Sea, or Gulf of Mexico. Many
of these remain over the ocean. However, about five hurricanes strike the United States
coastline every 3 years. Of these five, two will be major hurricanes (category 3 or
greater on the Saffir-Simpson Hurricane Scale).
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| What are some of the hazards associated
with hurricanes? |
Storm surge is a large dome of water often 50 to 100
miles wide that sweeps across the coastline near where a hurricane makes landfall. The
surge of high water topped by waves is devastating. The stronger the hurricane and the
shallower the offshore water, the higher the surge will be. Along the immediate coast,
storm surge is the greatest threat to life and property.
- Storm Tide
The storm tide is the combination of the storm surge and the normal astronomical tide. If
the storm surge arrives at the same time as the high tide, the water height will be even
greater.
- Winds
Hurricane-force winds, 74 mph or more, can destroy poorly constructed buildings and mobile
homes. Debris, such as signs, roofing material, siding, and small items left outside,
become flying
missiles in hurricanes. Winds often stay above hurricane strength well inland.
- Heavy Rains/Floods
Widespread torrential rains often in excess of 6 inches can produce deadly and destructive
floods. This is the major threat to areas well inland.
- Tornadoes
Hurricanes also produce tornadoes, which add to the hurricane's destructive power. These
tornadoes most often occur in thunderstorms embedded in rain bands well away from the
center
of the hurricane. However, they can also occur near the eyewall.
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| What areas are most likely to be hit by a
Hurricane? |
- All Atlantic and Gulf coastal areas are subject to
hurricanes or tropical storms. Although rarely directly struck by hurricanes, parts of the
Southwest United States and Pacific Coast suffer heavy
rain and floods each year from the remnants of hurricanes spawned off Mexico.
- Islands, such as Hawaii, Guam, American Samoa, and Puerto
Rico, are also subject to hurricanes. Due to the limited
number of evacuation routes, barrier islands are especially vulnerable to hurricanes.
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| Where can I find out more about
Hurricanes? |
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