HURRICANES
-1 BASICS
A hurricane is a type of tropical cyclone. In the Northern Hemisphere, there
is a counterclockwise circulation of winds. Hurricane winds
blow in a large spiral around a relative calm center known
as the "eye." The "eye" is generally 20 to 30 miles wide,
and the storm may extend outward 400 miles. They are
low-pressure systems. The eye of a hurricane is always a
low-pressure area. The lowest barometric pressures ever
recorded have occurred inside hurricanes.
Tropical cyclones are classified as follows:
Tropical Depression: winds of 38 mph.
Hurricane Fran 1996
Tropical Storm: winds of 39-73 mph.
Hurricane: winds of 74 mph or higher (120km/h).
Hurricane-like storms are called by different names in the different regions of
the world. For example, the name "hurricane" is given to systems that
develop over the Atlantic or the eastern Pacific Oceans. In the western North
Pacific and Philippines, these systems are called "typhoons" while in the
Indian and South Pacific Ocean, they are called "cyclones".
-2 FORMATION
The ingredients for a hurricane include warm tropical oceans, moisture,
wind. They can combine to produce violent wind, incredible waves,
torrential rain, and floods. Most Atlantic hurricanes begin off the west coast
of Africa, starting as thunderstorms that move out over the warm, tropical
ocean waters. The ocean water itself must be warmer than 26.5 degrees
Celsius (81°F). The heat and moisture from this warm water is the source
of energy for hurricanes. They will weaken rapidly when they travel over
land or colder ocean waters. Nevertheless a hurricane can extend inland for
hundreds of miles.
August and September are peak months during the hurricane season that
lasts from June 1 to November 30.
Hurricanes can spawn tornadoes
Floods are generated by torrential rains. They also cause damage and loss
of life.
Inland streams and rivers can flood and trigger landslides
Even more dangerous than the high winds of a hurricane is the
storm surge-a dome of ocean water that can be 20 feet at its peak and 50
to 100 miles wide. The surge can devastate coastal communities as it
sweeps ashore. Nine out of 10 hurricane fatalities are attributable to the
storm surge.
Each year, an average of ten tropical storms develop over the Atlantic
Ocean. 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 3year period, roughly five hurricanes strike the US 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.
If one percent of the energy in one hurricane could be captured, all the power,
fuel, and heating requirements of the United States could be met for an entire
year.
-3 CLASSIFICATION AND DAMAGE
Saffir-Simpson Hurricane Scale
Category
1
(119 to 1
2
(155 to 1
3
(178.6 to
4
(210 to 2
5
(> 249.4
Wind Speed
Effects
74 to 95 mph
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Storm surge 4 to 5 ft (1.2 to 1.5 m) above normal
Some flooding
No real damage to buildings.
96 to 110 mph
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Storm surge 6 to 8 ft (1.8 to 2.4 m) above normal
Trees down
Roof damage
Small boats grounded
111 to 130 mph
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Storm surge 9 to 12 ft (2.7 to 3.7 m) above normal
Structural damage in houses (damaged by floating debris).
Mobile homes destroyed
Severe flooding
131 to 154 mph
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Storm surge 13 to 18 ft (4 to 5.5 m) above normal
Severe flooding inland
Some roofs ripped off
Major structural damage
Major erosion of beach areas.
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Storm surge at least 18 ft (5.5 m) above normal
Severe flooding further inland
Serious damage to most wooden structures.
Flooding causes major damage to lower floors in houses ine.
Massive evacuation of residential areas may be required.
>155 mph
In a hurricane, the most violent winds occur in the area immediately around
the eye. Hurricanes produce significant damage and loss of life, mainly due to
flooding. When hurricanes move onto land, they can damage buildings, trees
and cars. The heavy waves are called a storm surge. Storm surge is very
dangerous and a major reason why you MUST stay away from the ocean
during a hurricane warning. The storm surge acts like a bulldozer sweeping
away everything in its path. The stronger the hurricane the higher the storm
surge will be.
Be sure to ask family members, friends and neighbours if they are
HURRICANE AWARE.
-4 HURRICANE PREPAREDENESS
Being hurricane smart means knowing what to do and having a safe place to go.
The key to hurricane protection is preparation. Preparation through education is less
costly than learning through tragedy.
You may want to talk with your neighbours to coordinate preparation plans
and help each other out.
Before hurricane season
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Plan an evacuation route or , if you’re staying, determine the safest
place in your home — an interior room, a hallway. Never decide to stay in
a mobile home.
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Don't be in a room with windows that can be broken.
If your house doesn't have a windowless room, you should at least stay
under a table or behind a sofa.
Once a window is broken, the wind blows inside to not only wreck the
interior, but also to apply upward pressure on the roof, which might be
enough to send it flying. If this happens, the walls collapse and your
house is flattened. Permanent shutters are the best protection.
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Have an evacuation or survival kit ready with nonperishable food, water,
a first aid kit and other things you'll need: cash and credit cards, and do
not forget your insurance policy!! You may need it!!
Make arrangements for pets. Pets may not be allowed into emergency
shelters for health and space reasons.
Take “before” pictures of your home for insurance claims.
Teach family members how and when to turn off gas, electricity, and
water.
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During a hurricane watch/ warning
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Have a battery-powered radio (to get the latest news).
Evacuate early if you live in a mobile home (to avoid traffic).
Fuel car.
Bring in outdoor objects such as lawn furniture, toys, garden tools,
mailbox and your garbage can (rubbish bin). The greatest threat to your
home in most hurricanes is not the wind itself but wind-blown debris that
can break windows and doors.
Remove outside antennas or satellite dishes.
Turn refrigerator and freezer to coldest settings. Open only when
absolutely necessary.
secure boat.
Reinforce the garage doors.
Park your car where it will be most protected if it must be outdoors
During the hurricane
At this stage your main priority is to remain calm and out of danger. Outside
your shelter raging winds are blowing torrential rain and battering your town. There is
no reason, unless in an absolute emergency, that one would need to venture outdoors.
Local officials have the authority to close roads and bridges.
Tips/Precautions:
• Stay indoors and away from windows.
• Stay tuned to radio (or TV if available) for weather bulletins.
• Use flashlights as a source of light.
• Candles can easily become a fire hazard
• Listen to local authorities.
° Avoid elevators (lifts)
After the hurricane
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Take pictures of the damage for insurance claims.
Drive only if absolutely necessary and avoid flooded roads.
Check for gas leaks.
Look for electrical system damage.
Check for sewage and water lines damage.
-5 NAMING AND FORECASTING
To better track hurricanes, weather officials decided to name them.
Until World War II, hurricanes were given only masculine names. In
the early 1950s, weather services began naming storms alphabetically and
with only feminine names. By the late 1970s, this practice was replaced
with alternating masculine and feminine names. The first hurricane of the
season is given a name starting with the letter A, the second with the letter
B and so on. According to NOAA, "the name lists... have an international
flavor because hurricanes affect other nations and are tracked by the public
and weather services of many countries."
Hurricanes in the Pacific Ocean are assigned a different set of names
than Atlantic storms.
In the early part of this century, coastal residents used to have
less than a day to prepare or evacuate their homes from an oncoming
hurricane. Today, these same locations receive warnings to evacuate from
one to two days in advance, let alone the extra days they are also aware of
its existence. Before satellites and radars, people had very little knowledge
of the weather just 100 kilometers offshore.