The El Niño weakened further in April 2016, approaching moderate-to-weak level based on April’s Niño3.4 sea-surface temperature (SST) readings (Figure A). The large-scale atmospheric responses to El Niño reflects its sustained weakening with the trade winds near the equatorial Pacific Ocean being near average and the cloud patterns there showing less of the typical El Niño characteristics. The Niño 3.4 index for April 2016 is 1.2 (Figure B) and the latest 3-month average (Feb-Apr) dipped from 2.3 to 1.8.
Over Southeast Asia, large-scale rainfall response to the El Niño in terms of widespread, drier-than-normal conditions was observed for April 2016 but mainly in the northern half of the region (Figure C). International climate models and expert assessment predict the end of El Niño by the middle of 2016 (Figure D). While there has yet to be consensus among experts if La Niña or neutral conditions are to occur in the second half of 2016, model outlook increasingly suggest that La Niña conditions are favoured more than neutral conditions (Figure E).
Impact of El Niño/La Niña on Southeast Asia
Typically the impact from El Niño for Southeast Asia is drier-than-normal rainfall conditions, especially for the southern parts of the region (Maritime Continent) during June to October. During La Niña events the opposite, i.e. wetter-than-normal, normally occurs (Figure F). Locally-specific impact differs from place to place and for different seasons.
The region is now in the inter-monsoon season (Mar-May) where the impact from El Niño is not as significant as the June to October period and is also limited to parts of the region between 0°-10°N (Figure G).
No two El Niño events or two La Niña events are alike in terms of their impact on the region’s rainfall and temperature. Furthermore, the strength of events and the corresponding impact do not always scale. For example, there were years where relatively weaker El Niño events induced more significant changes in rainfall than the stronger El Niño events.
- Figure A: The tropical Pacific Ocean continued to be warmer than usual over the Niño3.4 region (red box, 120°W-170°W and 5°S-5°N) in Apr 2016, but the warming is subsiding (image credit: IRI Map Room). Warm colour shades show regions of relative warming, while cool colour shades show regions of relative cooling with respect to 1971-2000 climatology for that month.
- Figure B: Monthly sea-surface temperature (SST) anomaly over the Niño3.4 region (120°W-170°W and 5°S-5°N) of the tropical Pacific Ocean from Apr 2015 to Apr 2016 (image credit: IRI Map Room). The El Niño is expected to end by mid-2016.
- Figure C: Spatial rainfall anomaly patterns in the region for Apr 2016 (image credit: IRI Map Room). Brown (green) colour shades show drier (wetter) than the average climatological rainfall for Jan (1970 – 2009). Widespread dry rainfall anomaly patterns are observed for the month over mainly the northern half of the region. Quantitative anomaly values are only indicative due to limitations in the data source.
- Figure D: Forecasts of El Niño strength (in terms of the Niño3.4 index) for 2016 from various seasonal prediction models of international climate centres. Temperature anomalies above 0.5°C indicate El Niño conditions, below -0.5°C indicate La Niña conditions, and in between indicate neutral conditions, i.e. neither El Niño nor La Niña. Models predict possibility of La Niña conditions occurring towards the end of 2016 but there is still considerable spread between neutral and La Niña conditions in the model outlook (image credit: IRI-CPC).
- Figure E: Probability of El Niño (red), La Niña (blue) and neutral conditions (green) for 2016. Neutral conditions are more likely to occur by the middle of 2016 while La Niña are increasingly more favoured than neutral conditions towards the end of 2016 (image credit: IRI-CPC).
- Figure F: June to October rainfall anomaly composite for La Niña years minus El Niño years. In general, green colour shades show regions where La Niña induce wetter conditions and El Niño induce drier conditions, while regions in brown shades show the opposite effect, i.e. La Niña inducing drier conditions and El Niño inducing wetter conditions (image credit: IRI Data Library). Note that the anomaly composite have been put together with limited number El Niño/La Niña occurrences between 1979 and 2015.
El Niño/La Niña
For El Niño/La Niña updates, MSS assesses information provided by the World Meteorological Organization (WMO) and various international climate centres, such as the Climate Prediction Center (CPC) US, the Bureau of Meteorology (BoM) Australia, as well information from the International Research Institute for Climate and Society (IRI) which contains model outputs from various other centres around the world. For more information on El Niño/La Niña, please refer to the FAQs website.
Frequently Asked Question
What is El Niño/La Niña and how do they affect weather in South East Asia?
In South East Asia, higher than normal rainfall tends to occur during a La Niña episode which may result in an increased occurrence of floods.
The correlation between El Niño/La Niña and its associated weather impacts on South East Asia differ from one place to another and for different seasons.
The image above shows the precipitation anomalies averaged over the El Niño and La Niña years. For instance, the impact of El Niño is typically stronger over the southern and eastern part of South East Asia during the months of Jun – Oct.