Why typhoon is not likely to hit Singapore

Storms usually move towards poles and away from the equator
Feng Zengkun Straits Times 30 Aug 11;

A TYPHOON that has hit Taiwan and the Philippines over the past few days is unlikely to strike Singapore, experts told The Straits Times.

This is because typhoons - also called cyclones or hurricanes in different parts of the world - usually move towards the poles and away from the equator.

They also usually form more than 10 degrees north and south of the equator, said Dr Adam Switzer, a National Research Foundation fellow and principal investigator at Nanyang Technological University's Earth Observatory of Singapore.

More than 61,000 people were evacuated from their homes in the Philippines over the weekend, after Typhoon Nanmadol, the strongest storm to hit the country this year, lashed the northern edge of the main island of Luzon, causing landslides and floods.

The 16 reported dead so far were buried in landslides, including two children who were killed in an avalanche of rubbish at their city's dumping grounds.

The typhoon then moved on to Taiwan and drenched it in 50cm of rain yesterday, before heading towards China.

No deaths have been reported in Taiwan so far.

A typhoon is essentially a storm spinning at great speed. Very few have occurred within 1.5 degrees - or 170km - of the equator in the phenomenon's recorded history. Singapore is about 137km north of the equator.

Scientists told The Straits Times that typhoons require water hotter than 26 deg C, a condition that can be found near the equator.

But they also require a natural phenomenon called the Coriolis effect, a result of the earth's rotation.

The effect, which produces the typhoon's extreme circular motion, is weakest near the equator. This means typhoons are extremely unlikely to form near the equator, the scientists said.

Typhoon Vamei, which hit eastern Malaysia in 2001, is a rare example in recorded history of a typhoon that formed near the equator. It caused $5.4 million worth of damage and killed five people.

This type of storm was previously thought to be impossible, and scientists at the Naval Postgraduate School in the United States concluded in their post- disaster report that it was caused by a perfect storm of factors, including the rare persistence of both a low pressure area and a cold surge in the region.

They estimated that a typhoon like that one was likely to happen only once every 100 to 400 years.

But scientists warned that although Singapore is not likely to be directly affected by typhoons, there are indirect costs.

These include the closure of international finance institutions such as the Hong Kong stock exchange, potential damage to overseas investments from Singapore companies and the loss of crops from overseas suppliers.

Dr Switzer said: 'In short, big typhoons are locally devastating and regionally important events, which often have global consequences in the future.'