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Typhoons: Asia's mega-storms
Typhoons are some of the most powerful and destructive storms seen anywhere in the world.
Last Modified: 10 Aug 2009 08:51 GMT
In this 1995 photo from the space shuttle the eye of Typhoon Angela is clearly visible [Nasa]

Typhoons are some of the most powerful and destructive storms seen anywhere in the world.

Similar storms are known as hurricanes when they occur in the Atlantic ocean or adjacent seas, and a cyclone or tropical cyclone in the Indian ocean region.

Peak typhoon season is usually from July to October, although they can occur at any time of year.

Areas worst hit by typhoons include the Philippines, eastern and southern coasts of China (including Hong Kong), Taiwan, the Korean peninsula, Japan and Vietnam.

Recent particularly deadly typhoons include Typhoon Fengshen, which left more than a thousand dead in the Philippines in June 2008.

Cyclonic effect

Typhoons bring a destructive combination of heavy rain and strong winds [Reuters]
Typhoons typically develop above the warm tropical seas of the Pacific about 10 degrees north of the equator, feeding on the heat released from rising moist air.

The rotation, or "cyclonic" effect, of the storm is generated by the spin of the Earth, which twists the system in an anti-clockwise direction – as opposed to a clockwise direction if a storm occurs in the Southern Hemisphere.

Typhoons usually bring heavy rains and powerful winds, around a still and clear area known as the "eye".

Once a cyclone reaches winds of at least 34 knots or 61kph, it is typically called a "tropical storm" and assigned a name.

If it intensifies to hit 64 knots or 118kph, a tropical cyclone becomes a typhoon.

Storm names

Typhoons generated over the Pacific regularly pound Asia between July and October [AFP]
Names for typhoons are decided in advance by a typhoon committee, consisting of meteorological organisations of 14 countries and regions in the Asia Pacific.

A new name is automatically chosen from the list when a typhoon is "born".

American-style names were used for typhoons until 2000, when Asian names began to be used.

Some countries, such as Japan, prefer to use number-based conventions and the Philippines has its own list of names for tropical cyclones, mainly used for domestic news and advisories.

While typhoons often cause massive damage and loss of life, scientists recently found that they may trigger slow earthquakes, acting as valves to slowly release stresses along fault lines in a non-violent manner over hours or days, to avoid the buildup of high stresses that could lead to a single great earthquake in a few explosive seconds or minutes.

A typhoon is a strong tropical cyclone that forms in the northwestern Pacific ocean.

Source:
Agencies
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