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WMO El Niño/La Niña Update

7 July 2017

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Current Situation and Outlook 

ENSO neutral conditions currently prevail in the tropical Pacific Ocean, despite sea surface temperatures being near the El Niño threshold. Most climate models surveyed indicate that ENSO-neutral conditions will continue through July-September 2017, followed by a 50-60% chance of a continuation of ENSO-neutral during the subsequent months of 2017. The development of El Niño conditions is slightly less likely, while the emergence of La Niña appears unlikely. National Meteorological and Hydrological Services will continue to closely monitor changes in the state of ENSO over the coming months.

Since late April, sea surface temperature anomalies in the east-central equatorial Pacific have been near +0.5˚C, approaching the threshold of El Niño conditions. However, atmospheric patterns have continued to reflect neutral ENSO conditions with a tendency towards above-average rainfall over the Maritime Continent, near to below-average rainfall in the central Pacific Ocean, and near-average to weakly reduced trade winds across portions of the tropical Pacific. Although reduced trade winds continue over the far eastern equatorial Pacific, the sea surface temperatures in that region have receded to average conditions from their strongly positive levels earlier in 2017. The temperature of the waters at depth, from the central Pacific eastward and extending several hundred meters below the surface, have been close to or slightly above average; these waters often provide some indication of the coming conditions at the surface. Although there is some warmth below the surface of the tropical Pacific Ocean, this warmth is not near El Niño levels.

Most dynamical models surveyed predict that sea surface temperatures in the east-central tropical Pacific Ocean will remain at ENSO-neutral levels over the next two months (averaging +0.3 °C), while statistical models favour a borderline El Niño (+0.5 °C). These slightly above-average, but still ENSO-neutral conditions are projected to persist until the end of 2017. Based on these predictions and expert assessment, the chance of ENSO-neutral continuing in the second half of 2017 is in the range of 50-60%, with the likelihood of El Niño somewhat lower at around 35-45%. There is very little chance of La Niña developing during the last half of 2017.

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).

In summary:

  • Although sea surface temperatures have been near the threshold of El Niño, the tropical atmosphere has been unresponsive, and therefore ENSO-neutral conditions continue;
  • Models surveyed and expert opinion suggest ENSO-neutral conditions are likely to continue through the remainder of 2017. Chances of ENSO-neutral are in the predicted range of 50-60% during the second half of 2017, while El Niño development is the next most likely scenario, with only a very small chance for La Niña.
  • The state of ENSO will continue to 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 National Meteorological and Hydrological Services.

For web links of the National Meteorological Hydrological Services, please visit:

https://public.wmo.int/en/about-us/members

For information and web links to WMO Regional Climate Centres please visit:

http://www.wmo.int/pages/prog/wcp/wcasp/RCCs.html

An archive of all WMO El Niño/La Niña Updates issued so far, including this one, is available at:

http://www.wmo.int/pages/prog/wcp/wcasp/enso_updates.html

 





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