Kezia Toh Straits Times 28 Oct 11;
EXPECT more rain in the days ahead, the National Environment Agency (NEA) has said.
Singapore has experienced a recent wet spell and yesterday's heavy rain once again caused flash floods - this time in Shenton Way.
This month marks the start of the second inter-monsoon period of the year, said an NEA spokesman, which leads to the north-east monsoon months of November, December and January.
Referring to long-term statistics at its climate station, NEA said October is a relatively wet month.
The wettest months for Singapore are December, November and January, followed by October.
NEA does not have complete rainfall figures for this month because October has not ended. The highest one-day rainfall recorded in October is 209.4mm in 2001.
The long-term average rainfall for October is 193.7mm.
The inter-monsoon period is characterised by weaker winds that do not come from a fixed direction, hence accounting for the more erratic weather.
Assistant Professor Koh Tieh Yong from the School of Physical and Mathematical Sciences at Nanyang Technological University said this is when south-west winds meet north-east winds, bringing moisture to the region.
As Singapore was in the zone of convergence along the Malay peninsula over the last two weeks, it led to wet weather and flash floods in places such as Little India and Serangoon.
It also explained yesterday's deluge which flooded two lanes of Shenton Way at about 1pm.
Water agency PUB said the overflow subsided in about 20 minutes and the cause of the flash floods is being investigated.
Meanwhile, experts said short spurts of intense rainfall are also on the radar.
'This is because of individual storm systems - parcels of air that are sufficiently hot that they would leave the surface and rise,' said Prof Koh.
'As they rise, they will cool and water vapour condenses, eventually forming rain,' he added.
Associate Professor Matthias Roth of the National University of Singapore's geography department also noted that there is a tendency towards more 'intense, short-lived rainfall events'.
'We can expect more rain as we enter the north-east monsoon season,' he said.
Heavy rain has also pelted the region.
Severe flooding this year has killed more than 1,000 people across Asia, with economic losses running into the tens of billions of dollars.
Thailand is suffering its worst flooding in 50 years.
But Prof Roth said more data is needed before one can point the finger at global warming.
'We need more data before we can conclusively link this to climate change or global warming - 20 to 30 years of data, not just two or three; though the somewhat extreme events we currently experience fit weather predictions in a warmer world.'
