Neutral conditions (neither El Niño nor La Niña) continue in the tropical Pacific. Model forecasts and expert opinion suggest that the likelihood of El Niño or La Niña conditions developing during the first half of 2013 is low, and that neutral conditions are likely to be maintained through the boreal spring. National Meteorological and Hydrological Services and other agencies will continue to monitor Pacific Basin conditions and provide outlooks to assess the most likely state of the climate through the coming several months of 2013.

During the last 10 months El Niño-Southern Oscillation (ENSO) indicators in the tropical Pacific (e.g., tropical Pacific Ocean temperatures, sea level pressure, cloudiness and trade winds) have generally been at neutral levels, indicating neither El Niño nor La Niña conditions have been present. From July to October 2012, sea surface temperatures increased to a borderline El Niño level, but the atmospheric characteristics of El Niño failed to develop and the ocean-atmosphere system as a whole remained in a neutral state. Since November the tropical Pacific Ocean has cooled, and although the first two months of 2013 showed patterns of ocean temperatures that approached borderline La Niña levels, and cloudiness and trade winds that also leaned towards La Niña conditions, the tendency has been weak and the state of the ocean-atmosphere system as a whole continued to be neutral.

The latest outlooks from climate models and expert opinion suggest that sea surface temperature and atmospheric anomalies are most likely to remain neutral through the boreal spring of 2013. Less than a quarter of models surveyed predict borderline or weak La Niña conditions during the February to April period, but nearly all models clearly display neutral conditions by early boreal spring. No model predicts El Niño development during the period of March to May 2013. Forecasts beyond the boreal spring made at this time of the year have lower levels of skill than outlooks made at other times; hence users should factor this into their risk assessments.

It is important to note that El Niño and La Niña are not the only factors that drive global climate patterns. At the regional level, seasonal outlooks need to assess the relative impacts of both the El Niño/La Niña state and other locally relevant climate drivers. Such other factors may include, for example, conditions in the tropical Indian and Atlantic oceans, as these can influence surrounding continental climate patterns. Locally applicable information should therefore be consulted in detailed regional/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:

Since April 2012, conditions have remained neutral in the tropical Pacific (neither El Niño nor La Niña);
Since January 2013 tropical Pacific Ocean temperatures and some atmospheric features have leaned toward La Niña conditions, but the overall ocean-atmosphere system has remained neutral;
As of late February 2013, outlooks indicate that neutral conditions are likely to continue through the boreal spring, after which the outlook is uncertain due to characteristically low outlook confidence at this time of the year.

The situation in the tropical Pacific will continue to be carefully monitored. More detailed interpretations of regional climate fluctuations will be generated routinely by the climate forecasting community over the coming months and will be made available through the National Meteorological and Hydrological Services. For web links of the National Meteorological Services, please visit:

http://www.wmo.int/pages/members/members_en.html