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The science of hurricanes


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#1    Talon

Talon

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Posted 15 September 2004 - 12:32 AM

The science of hurricanes

Hurricanes are natural phenomena and have been storming the globe for thousands of years.
They are important features of the Earth's atmosphere as they transfer heat and energy from the equator to the poles.

However, when these natural hazards come into contact with people and their environments, they can cause much devastation and loss of life.

A hurricane is a large rotating storm centred on an area of very low pressure, with wind speeds in excess of 119km/h (74mph).

For a hurricane to form several conditions must be fulfilled:

Sea surface temperatures greater than 26C
Rapidly cooling air above
A sufficient spin from the rotating Earth.
As the warm sea heats the air above it, a current of warm moist air rises up quickly, creating a centre of low pressure at the surface.
Trade winds rush in towards the low pressure area and inward spiralling winds whirl upwards releasing heat and moisture.

The rotation of the Earth causes the column to twist around the eye which remains calm and free from clouds.

Late start

This season started rather quietly.

There were no hurricanes and only one tropical storm (winds 90-100km/h; 55-63mph) in the months of June and July, compared with 2003 where two hurricanes and six storms had already occurred.

August, however, was a different story.

Four hurricanes and four tropical storms formed, with four of them hitting the Caribbean or the US.

Storms such as Charley and Frances had long, warm sea tracks allowing them to gain moisture and energy as they made their way towards land.

With Ivan being the fifth hurricane to hit such areas, it could be said in summary that after a late start, this season is surely shaping up to be a stormy one, and there are still two months to go.

Global warming

In fact, the 2003 season was also very active, but very few storms made landfall and so there was little media attention.

Another issue recently at the forefront of media attention is global warming.

The likely rise in global temperatures has often been linked with the increasing frequency and ferocity of worldwide storms.

It could be said that a rise in sea surface temperatures will surely increase the area where these storms can form, therefore it is likely to increase the frequency of such hazards.

However, there are many areas which currently have sea temperatures of over 26C which do not spawn hurricane development.

There are in fact so many other factors which influence the development of hurricanes, such as the influence of El Nino, seasonal Saharan rainfall, wind shear, to name a few, that it is very difficult to pinpoint any effect that global warming might have.

As to whether hurricanes are stronger and more destructive than in the past, many factors must be taken into account and it is often very hard to gauge.

Natural hazards

The strength of the hurricane, the loss of life, the cost to property and infrastructure, and the areas which are hit must all be measured.

A hurricane's strength is measured on a scale of 1 to 5; 5 being the strongest wind strength around the eye.

A look back into the history books shows that the number of category 5 storms in the Atlantic Ocean has not increased in recent years.

In terms of loss of life, the deadliest hurricane occurred in 1900, when 8,000 people were killed, mainly in Texas.

This was mostly due to the lack of preparedness and technical advancement in understanding such storms.

The costliest of hurricanes, however, occurred in 1992. Hurricane Andrew (a category 5 storm) swept through one of the most densely populated areas of Florida.

Over $25bn worth of damage was caused, but because of advances in forecasting, computer and satellite technology, timely warnings meant that fewer than 100 deaths were recorded.

Hurricanes are essential natural hazards. But with ever larger numbers of people moving to the attractive coastal areas of tropical regions, can technological advancement improve forecasts enough to keep loss of life and injury down to a minimum?

http://news.bbc.co.uk/1/hi/sci/tech/3653020.stm


"Wise men talk because they have something to say; fools, because they have to say something." -Plato




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