SINGAPORE (The Straits Times/ANN): Two different rain-bearing climate phenomena are expected to be felt in Singapore by December, when the country usually experiences its wettest weather.
But their arrival may not increase total rainfall over Singapore during the year-end holidays, experts told The Straits Times, as these events tend to influence rainfall during other parts of the year instead.
The Republic’s usual rainy season in December and January is caused by the wet phase of the north-east monsoon, when winds blow from the cool Northern Hemisphere towards the equator.
This period will also usually see one to three episodes of monsoon surges, which results in higher rainfall over Singapore, as was the case in January.
These surges refer to bursts of cold air from the north-east, such as Central Asia. As the cool air flows over the warm waters of the South China Sea, it picks up moisture, bringing widespread rainfall, strong winds and cooler weather to Singapore.
But ST checks show that in 2025, the rainy season will coincide with the return of La Nina and the negative phase of the Indian Ocean Dipole (IOD).
Both climate phenomena tend to result in higher rainfall over Singapore, owing to changes in atmospheric pressure and sea surface temperatures across the Pacific and Indian oceans. The Republic sits between both ocean basins, and can be influenced by weather patterns there.
The Meteorological Service Singapore under the National Environment Agency noted on its website that Singapore is on “La Nina watch”, which it says is expected to persist until at least the end of 2025.
In response to ST’s queries, a spokesperson for the Met Service said it is likely that La Nina conditions have already been established, based on preliminary assessments of sea surface temperatures in October.
Separately, the Met Service also noted on its website that a negative IOD is present, and that it is expected to persist until December.
