There is a 50-60% chance of an El Niño event forming in middle to late 2017, according to a new Update from the World Meteorological Organization.
The El Niño/Southern Oscillation (ENSO) is a naturally occurring phenomenon involving fluctuating ocean temperatures in the central and eastern equatorial Pacific, coupled with changes in the atmosphere. It has a major influence on weather patterns in many parts of the world and has a warming impact on global air temperatures.
Following borderline weak La Niña/cool-neutral conditions during the second half of 2016, sea surface temperatures and most atmospheric fields returned to more ENSO-neutral levels in January 2017 that continued to the present.
However, sea surface temperatures in the far eastern tropical Pacific Ocean increased to 2.0° Celsius or more above average during February and March, creating very heavy rainfall and a trade wind collapse from the Galapagos Islands to the coasts of Ecuador and Peru. This localized warming – known in Peru as a “coastal El Niño” - is different from the more broadly known El Niño warming pattern, but its impacts on the affected areas were just as big.
Many of the climate models surveyed indicate that basin-wide neutral conditions will persist through to June 2017. The subsequent development of an El Niño during the second half of 2017 is more likely than the continuation of neutral conditions. The emergence of La Niña appears very unlikely, according to the Update, which is a consensus-based product, based on contributions from leading centres around the world that monitor and predict this phenomenon, and expert assessment of the results of climate models.
It should be kept in mind that predictions of ENSO made before May or June for the second half of the year typically have less certainty than outlooks made later in the year.
“Memories are still fresh of the powerful 2015-2016 El Niño which was associated with droughts, flooding and coral bleaching in different parts of the world and which, combined with long-term climate change, lead to increase of global temperatures to new record highs in both 2015 and 2016,” said Maxx Dilley, director of WMOs Climate Prediction and Adaptation division.
“Accurate predictions of the most recent El Niño saved untold lives. Our greatly improved ability to forecast El Niño and La Niña events contributes to the public good and is essential for the agricultural and food security sectors, for management of water resources and public health, as well as for disaster risk reduction,” said Mr Dilley.
The effects on regional climate of each El Niño event are never exactly the same: they depend on the intensity of the event, the time of year when it develops and the interaction with other climate patterns.
It is important to note also that El Niño and La Niña are not the only factors that drive global climate patterns. For example, sea surface temperatures of the Indian Ocean, the southeastern Pacific Ocean and the Tropical Atlantic Ocean are also known to influence the climate in the adjacent land areas.
The state of ENSO will be carefully monitored. More detailed interpretations of regional climate variability will be generated routinely by the climate forecasting community over the coming months and will be made available through the WMO Regional Climate Centres and National Meteorological and Hydrological Services.
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El Niño is often associated with warm and dry conditions in southern and eastern inland areas of Australia, as well as Indonesia, the Philippines, Malaysia and central Pacific islands such as Fiji, Tonga and Papua New Guinea. During the northern hemisphere summer season, the Indian monsoon rainfall generally tends to be less than normal. In the northern hemisphere winter, drier than normal conditions are typically observed over south-eastern Africa and northern Brazil.
Wetter than normal conditions are typically observed along the Gulf Coast of the United States, the west coast of tropical South America (Colombia, Ecuador and Peru) and from southern Brazil to central Argentina. Parts of eastern Africa (Kenya, Uganda) also usually receive above-normal rainfall. El Niño is associated with milder winters in north-western Canada and Alaska due to fewer cold air surges from the Arctic – a result of a large-scale region of lower pressure centred on the Gulf of Alaska/North Pacific Ocean.
A WMO animation on El Niño is available here