Four Hurricanes In 5 Weeks
What, Exactly, Is Going On?

By Michael McCarthy
The Independent - UK
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.
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:
What is a hurricane?
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.
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.
How is a hurricane formed?
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.
Why are its effects so severe?
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.
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.
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.
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.
How are hurricanes graded?
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:
Category one (minimal): winds 75 to 95mph, minor flooding, slight structural damage, storm surge up to 1.5 metres.
Category two (moderate): winds between 96 and 110mph, roof and tree damage, storm surge 1.8 to 2.4m.
Category three (extensive): winds between 111 and 130mph, houses damaged, severe flooding, storm surge 2.7 to 3.7m
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.
Category five (catastrophic): winds above 155mph, many buildings destroyed, smaller ones blown away completely, severe inland flooding, storm surge of more than 5.5m.
How do the 2004 hurricanes measure up?
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.
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.
Are hurricanes getting worse or more frequent?
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.
Why and how are hurricanes named?
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.)
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.
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.
The Year of the Hurricane
Hurricane Charley: 'The wrecking ball'
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.
Estimated cost of damage: $7-8bn.
Hurricane Frances: 'The size of Texas'
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.
Estimated cost of damage: much less than Charley, but still between $2bn and $4bn.
Hurricane Ivan: The most powerful
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.
Estimated cost of damage: still too early to assess.
Tropical Storm Jeanne: The biggest killer
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.
Estimated cost of damage: still too early to assess.
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