Grace Chua Straits Times 13 Oct 11;
A SPATE of early-morning squalls has toppled trees from Ang Mo Kio to Pulau Hantu, but experts said the wet and windy weather is not unheard-of for this time of year.
On Tuesday, an uprooted tree at Lower Delta Road fell and hit a taxi, trapping its driver inside until Singapore Civil Defence Force officers could free her.
Last week, towering casuarina trees on the southern island of Pulau Hantu were uprooted by strong winds, startling National University of Singapore researchers there to conduct studies.
The National Environment Agency (NEA) said the bad weather was due mainly to Sumatra squalls - lines of thunderstorms moving east - which are common during the south-west and inter-monsoon periods and are often accompanied by wind gusts of 40kmh to 80kmh.
In fact, during Sumatra squalls this month, wind gusts as strong as 80.6kmh were detected, the NEA said.
On two other days, Thursday and Friday last week, heavy rain was due to thunderstorms induced by strong heating of land areas in the afternoon.
An NEA spokesman explained that such intense thunderstorms could take place at any time of the year and tended to be unpredictable and sudden.
In all, 26 roadside trees were uprooted during eight days of intense rain, a spokesman for the National Parks Board (NParks) said.
The fallen trees were in Bukit Timah, Lower Delta, South Buona Vista, Holland, Bedok, Ang Mo Kio, Neo Tiew, Hougang and Craig Road.
But NParks has stepped up its tree inspections and pruning of mature trees since last May, especially in places with a lot of vehicle traffic, said Mr Simon Longman, the agency's director of streetscape.
Climate scientist Koh Tieh Yong of the Nanyang Technological University said of the wet weather: 'I wouldn't say it is unusual. Weather is never a constant but, nowadays, there is heightened public interest in it. I don't think the recent weather is cause for alarm per se.'
Assistant Professor Koh, who heads the university's tropical atmosphere research group, explained that October to November is a transition period, like a 'tug of war' between the south-west and north-east monsoon wind systems.
The convergence of the two carries rain, and typically reaches Singapore around December.
At the moment, the two fronts are pushing against each other near Vietnam, and this partly accounts for the heavy rain and floods in Thailand, Vietnam and Cambodia.
