Wild Weather
hurricanes
hurricane Fran
introduction
BASICS
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A hurricane is a type of tropical cyclone.
In the Northern Hemisphere, there is a
counter clockwise circulation of winds.
Hurricane winds blow in a large spiral
around a relative calm centre 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.
classification
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Tropical cyclones are classified as
follows:
Tropical Depression: winds of 38
mph.
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.
The ingredients for a hurricane
FORMATION
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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.
Hurricane Danger
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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.
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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 3-year 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 SaffirSimpson 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.
CLASSIFICATION AND
DAMAGE
Saffir-Simpson Hurricane Scale
Saffir-Simpson Hurricane Scale
egory
1
Cat
Wind Speed
74 to 95 mph
Effects
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2
96 to 110 mph
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3
111 to 130 mph
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4
131 to 154 mph
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5
>155 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.
Storm surge 6 to 8 ft (1.8 to 2.4 m) above normal
Trees down
Roof damage
Small boats grounded
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
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.
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
Massive evacuation of residential areas may be required
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.
HURRICANE
PREPAREDENESS
Be sure to ask family members, friends and neighbours if
they are hurricane aware.
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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.
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.
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.
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 windblown 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
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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
NAMING AND FORECASTING
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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 flavour 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.
forecasting
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 kilometres offshore.