Expect rain this month, but hot weather to follow

Singapore is likely to have more showers for the rest of the month, but the weather after that could become drier and hotter than usual.

The National Environment Agency (NEA) said in its latest forecast that the country can expect four to five days of short, thundery showers in the late morning and early afternoon in the second half of the month.

In addition, there may be one to two days of downpours with gusty winds in the pre-dawn hours and morning, as well as a slight haze on a few days.

Singapore and other southern ASEAN countries such as Indonesia and Malaysia typically have drier weather from next month to September. But this year, Singapore is more likely than not to be hit by a weather phenomenon called El Nino, which could make the country even hotter and drier during those months.

During an El Nino event, a warm pool of water in the western Pacific Ocean sloshes eastwards, triggering thunderstorms that move away from South-east Asia towards the United States and South America.

During the "strong" El Nino in 1997, Singapore's rainfall from June to September was about half the usual average.

This year, there is a 60 to 70 per cent chance of a "weak" El Nino developing by summer in the northern hemisphere, which is from late June to late September, the NEA said.

The forecast was based on the Meteorological Service Singapore's assessment of computer model outlooks from international climate centres.

Some of the models also point to the possibility of a moderate El Nino towards the end of this year.

The NEA cautioned, however, that the predictions could be off the mark, since the models cannot "skilfully" capture El Nino at this time of the year.

Weather experts said that between March and this month, as the northern hemisphere transitions to summer, the ocean-atmosphere system in the part of the Pacific Ocean relevant to El Nino is in transition. This makes it difficult for computer models to predict El Nino.

Winston Chow from the National University of Singapore's Department of Geography said: "The ocean-atmosphere system becomes more stable once summer happens.

"Once the relevant data such as sea surface temperatures and wind speed and direction from the end of this month onwards is fed into the models used to forecast El Nino, the predictions should become more confident."

However, Nanyang Technological University's Koh Tieh Yong said data showed there has already been a weak El Nino since last September, and he believes the El Nino will remain weak until at least the end of next month.

But Associate Professor Koh agreed with Assistant Professor Chow that predictions for the longer term are too uncertain at this point.

zengkun@sph.com.sg

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