WMO El Niño/La Niña Update
28 April 2017
Neutral El Niño/Southern Oscillation (ENSO) conditions currently exist in the tropical Pacific Ocean. However, in the far eastern tropical Pacific during February and March, strong ocean warming, combined with a collapse of the trade winds, resulted in localised severe impacts in Peru and adjacent countries. This strong warming event has now weakened. Most climate models surveyed indicate that basin-wide ENSO-neutral conditions will persist through April-June 2017, followed by a 50-60% chance of El Niño development in the subsequent months. The continuation of ENSO-neutral conditions is slightly less likely, while the emergence of La Niña appears remote. National Meteorological and Hydrological Services will continue to closely monitor changes in the state of ENSO over the coming months.
Following weak La Niña-like ENSO conditions during the second half of 2016, sea surface temperatures and most atmospheric fields have persisted at ENSO-neutral levels since January 2017. However, sea surface temperatures in the far eastern tropical Pacific Ocean increased to 2.0 degrees Celsius or more above average during February and March, creating localized heavy rainfall and a trade wind collapse from the Galapagos Islands to the coasts of Ecuador and Peru. This localized warming is distinct from the more broadly known El Niño warming pattern, and does not necessarily mean that a basin-wide El Niño event will develop later this year.
Currently, sea surface temperatures in the central tropical Pacific are close to average, but are accompanied by cloud patterns more typical of a La Niña-like state. The Niño 3.4 region in the east-central tropical Pacific Ocean has warmed to average to slightly above average temperatures during the last two months. The temperature of the waters at depth, from the central Pacific eastward and extending several hundred meters below the surface, have also been close to average; these waters often provide some indication of the coming conditions at the surface.
Most dynamical and statistical prediction models surveyed predict that sea surface temperatures in the east-central tropical Pacific Ocean over the next two months will warm, but remain neutral. Beyond May, models suggest a variety of possible scenarios, ranging from neutral conditions to a moderate El Niño, but overall favor El Niño development. Average dynamical model predictions indicate sea surface temperatures in the east-central tropical Pacific peaking at about 1.0 to 1.2 degrees Celsius above average during the third and fourth quarters of 2017, while the average for the statistical models is about 0.5 to 0.7 degrees Celsius above average. It should be kept in mind that predictions of ENSO for the second half of the year, made before May or June, typically have less certainty than outlooks made later in the year. Based on these predictions and expert assessment, the chance of El Niño developing in the second half of 2017 is in the range of 50-60%, with the likelihood of ENSO-neutral somewhat lower at around 40%. There is very little chance of La Niña during 2017.
A careful watch will be maintained on the oceanic and atmospheric conditions in the tropical Pacific Ocean in the coming months to assess the possible transition to El Niño.
It is important to note that El Niño and La Niña are not the only factors that drive global climate patterns, and that the strength of ENSO does not automatically correspond to the strength of its effects. At the regional level, seasonal outlooks need to assess the relative effects of both the El Niño/Southern Oscillation state and other locally relevant climate drivers. 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. Regionally and locally applicable information is available via regional and national seasonal climate outlooks, such as those produced by WMO Regional Climate Centres (RCCs), Regional Climate Outlook Forums (RCOFs) and National Meteorological and Hydrological Services (NMHSs).
- ENSO-neutral conditions are currently in place;
- A strong sea surface temperature warming and trade wind collapse occurred in the far eastern tropical Pacific Ocean during February and March, producing heavy rainfall in coastal Peru and adjacent countries;
- Models surveyed and expert opinion suggest ENSO-neutral conditions are likely to continue through most of the second quarter of 2017, with some possibility of El Niño development around the middle of the year;
- Models and expert opinion suggest chances for El Niño have increased and are in the range of 50-60% during the second half of 2017; ENSO-neutral conditions are the next most likely scenario, with only a very small chance for La Niña.
- Longer-range ENSO forecasts issued prior to June for the second half of the year have less certainty than those issued in the second half of the year.