- Is 2004 the Year of the Hurricane? It depends on where
you're considering it from. If you live in the US you'll certainly think
so, because the state of Florida has been struck by three in a month, and
as America dominates the world's media, the story has had huge attention
right around the globe. And now a fourth storm has devastated parts of
the Caribbean.
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- However, although to have three tempests of the intensity
of hurricanes Charley, Frances and Ivan burst through one state in the
space of four weeks is certainly unusual, the fact that all three made
landfall so close together in time and space may well be pure chance.
Hurricanes
sweep the oceans every year. So here are some of the questions that the
2004 hurricane season throws up, with some of the answers:
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- What is a hurricane?
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- A hurricane is a tropical cyclone, an area of intense
low pressure in the tropics surrounded by a violent rotating storm. It
is called a hurricane in the North Atlantic, the Northeast Pacific east
of the dateline, and the South Pacific Ocean east of 160E; west of the
dateline it is called a typhoon, and in the Indian ocean, a cyclone.
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- It becomes a hurricane officially if its wind speeds
reach 75mph, or force 12 on the Beaufort scale; below that it is a tropical
storm. Every year, there are about 100 tropical storms and about 50 of
them reach hurricane strength. The name comes from "Hurican",
the Carib god of evil.
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- How is a hurricane formed?
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- Hurricanes need precise meteorological conditions to
form: the sea surface temperature needs to be above 26.5C. They are powered
by the heat energy released by water vapour: the air above warm tropical
water rises quickly as it is heated by the sea, and as it does so it
rotates
or spins, creating an area of very low pressure, which becomes the eye
of the storm. Around the eye winds grow with great velocity, generating
violent seas.
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- Why are its effects so severe?
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- First, hurricanes produce the highest wind speeds, up
to 200mph in the most extreme cases, which only the strongest structures
can withstand. Second, they produce absolutely enormous amounts of rain
which can lead to catastrophic flash floods. But third - and sometimes
most seriously - they produce a phenomenon known as a storm surge. This
is a huge raising of the sea level, caused jointly by the huge winds and
the very low atmospheric pressure. In the most extreme cases it can be
as much as 25ft above normal.
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- The hurricane pushes this heightened sea along in front
of its path and when it hits the coastline, especially the low-lying
coasts,
there can be disastrous inundations, especially when the surge combines
with torrential rain.
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- Britain experienced something like this on 30 January
1953 when a violent gale combined with very low pressure produced a storm
surge in the North Sea, which breached the sea defences of Lincolnshire
and East Anglia and drowned 307 people.
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- Once a hurricane reaches land, it tends to die out fairly
quickly as there is no more warm water to supply heat. But out in the open
ocean it can last for a fortnight or more.
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- How are hurricanes graded?
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- Hurricanes are now measured between strengths 1 and 5
on the Saffir-Simpson scale, formulated in 1969 by Herbert Saffir, a
consulting
engineer, and Dr Bob Simpson, the director of the US National Hurricane
Centre. The scale was devised in the aftermath of Hurricane Camille in
1969, the most violent storm ever to hit the continental United States.
Its categories run like this:
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- Category one (minimal): winds 75 to 95mph, minor
flooding,
slight structural damage, storm surge up to 1.5 metres.
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- Category two (moderate): winds between 96 and 110mph,
roof and tree damage, storm surge 1.8 to 2.4m.
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- Category three (extensive): winds between 111 and 130mph,
houses damaged, severe flooding, storm surge 2.7 to 3.7m
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- Category four (extreme): winds of between 131 and 155mph,
major structural damage to houses and some roofs destroyed, storm surge
of between 4 and 5.5m.
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- Category five (catastrophic): winds above 155mph, many
buildings destroyed, smaller ones blown away completely, severe inland
flooding, storm surge of more than 5.5m.
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- How do the 2004 hurricanes measure up?
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- The three storms that hit Florida this summer were pretty
bad, but not among the worst on record: their intensity was actually feared
to be worse than it turned out to be. Frances was a category two/three
and did the least damage; Charley was a three/four, and Ivan a category
four occasionally touching five.
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- But they did not compare in destruction with Hurricane
Andrew, the category four/five storm that struck Florida in August 1992,
which caused $25bn (£14bn) worth of damage at today's prices, or
in sheer power with Hurricane Camille, which struck Mississippi in 1969
leaving 256 dead, or the Labour Day Hurricane of 1935 which hit the Florida
Keys, killing 423. These latter two storms, full category fives, had winds
that approached 200mph and there has been nothing else like them in the
United States meteorological record.
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- Are hurricanes getting worse or more frequent?
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- Although global warming is confidently expected to
produce
more violent storms, scientists cannot yet prove a link between current
hurricane rates and climate change. There does not seem to have been an
increase in the number of category five hurricanes world-wide. This year
appears to be more active than 2003 and 2002 but less active than the four
years before that.
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- Why and how are hurricanes named?
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- All tropical cyclones are named, to provide ease of
communication
between forecasters and the general public about forecasts, watches, and
warnings. Since the storms can often be long-lasting and more than one
can be occurring in the same region at the same time, names can reduce
the confusion about which storm is being described. Before the 20th
century,
especially in the Caribbean, hurricanes were sometimes named after the
saint's day on which they struck land. During the Second World War, US
Navy meteorologists gave them the female names of wives and loved ones,
but by 1950 a formal naming strategy was in place for North Atlantic
cyclones,
based on the phonetic alphabet of the time (Able, Baker, Charlie and so
on.)
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- In 1953 the US Weather Bureau decided to switch to female
first names, and with the agreement of the World Meteorological
Association,
included male first names in the list in 1979.
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- Each meteorological region of the world now has an agreed
list of names. The letters Q, U, X, Y, and Z are not used because few names
begin with these letters. Quite a few hurricane names - including Andrew,
Betsy, Bob, Camille, Hugo and Hilda - have been officially retired because
the storms concerned caused damage on a scale unlikely to be repeated.
About 50 names have been retired: a country can request retirement.
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- The Year of the Hurricane
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- Hurricane Charley: 'The wrecking ball'
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- Hurricane Charley struck Florida on its eastern Gulf
coast on Saturday 14 August after two million people had been evacuated
from the Tampa area. Forecasters had estimated that this was where it would
hit first, but in fact it made landfall 100 miles further south and then
cut a diagonal swath of destruction 30 miles wide right across the state.
In total, 27 people were killed. The category four storm, described by
a rescue worker as "a wrecking ball that swung in at 145mph",
cut the power to 900,000 Florida homes and severely damaged about 40,000
buildings, especially in the Orlando area. Reconstruction and rehousing
programmes have been slow, because of subsequent hurricane alerts and
evacuations.
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- Estimated cost of damage: $7-8bn.
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- Hurricane Frances: 'The size of Texas'
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- Hurricane Frances hit Florida on its other side, the
eastern Atlantic coast, three weeks after Charley, on Saturday 4 September,
blowing ashore about 30 miles north of West Palm Beach. Twice as big as
Charley in area (as big as the state of Texas), even more people fled from
Frances - 2.4 million, the biggest evacuation in Florida's history. Frances
was the worst storm ever to hit the Kennedy Space Centre at Cape Canaveral,
left, which suffered superficial damage. In the event, its winds lessened
in strength and the eventual category three storm was much less destructive
of life and property, although four million people were left without power.
No one died.
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- Estimated cost of damage: much less than Charley, but
still between $2bn and $4bn.
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- Hurricane Ivan: The most powerful
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- To date, Hurricane Ivan has been the most powerful of
the 2004 hurricanes and was billed as the worst to hit the Caribbean for
10 years. At times a category five storm with 150mph winds, Ivan caused
at least 70 deaths in a "10-day tour" of the Caribbean islands
before striking the continental United States. It burst upon an unprepared
St George's, capital of Grenada, on Tuesday 7 September, leaving 34 dead
and destroying most of the town's buildings. It then went on to devastate
parts of Jamaica before hitting the Cayman islands on 11 September. It
eventually hit the Alabama coast and the Florida panhandle last Thursday
and has caused a total of 49 deaths in five US states.
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- Estimated cost of damage: still too early to
assess.
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- Tropical Storm Jeanne: The biggest killer
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- Not as turbulently powerful as the other hurricanes,
Tropical Storm Jeanne has been the cause of the highest number of
casualties.
It first struck Hispaniola - the island containing the Dominican Republic
in the east, and Haiti in the west, at the weekend, killing more than a
dozen people. Disastrous floods, fuelled by torrential rain, killed another
250 or more in Haiti according to the latest United Nations estimate; many
in the northern city of Gonaives. However, the extensive deforestation
in Haiti is believed to have made the flooding much worse and scores of
people are still missing after their houses were swept away. Jeanne has
now moved off north-east of the Bahamas, and is unlikely to hit the
US.
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- Estimated cost of damage: still too early to
assess.
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- ©2004 Independent Digital (UK) Ltd. All rights
reserved
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- http://news.independent.co.uk/world/environment/story.jsp?story=563983
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