WMO El Niño/La Niña Update
16 March 2015
Current Situation and Outlook
Since late October 2014, sea surface temperatures in the tropical Pacific Ocean have remained at near-borderline to weak El Niño levels. However, many atmospheric features of El Niño have displayed only weak or short-lived responses to the warming. For example, the pattern of cloudiness and rainfall anomalies has not been well defined. Models and expert opinion suggest a continuation of warm-neutral to weak El Niño conditions through April and May of 2015.
Most models suggest tropical Pacific temperatures will exceed El Niño thresholds toward the middle of the year. However, many models currently show a substantial spread in their outlooks for tropical Pacific Ocean temperatures, consistent with the known period of lower skill in longer lead predictions made at this time of year. This spread indicates that a range of outcomes remain possible, from neutral to a substantial El Niño event. This spread will narrow in the coming months as skill levels increase. National Meteorological and Hydrological Services and other agencies will continue to monitor Pacific Ocean conditions for further El Niño developments, and will assess the most likely local impacts.
As of early March, there have been more than five months when east-central tropical Pacific Ocean surface temperatures have ranged been 0.5° to 1.0° Celsius above average, which would typically indicate borderline to weak El Niño ocean conditions. However, despite this oceanic warmth, atmospheric indicators of El Niño have been weak or have appeared only intermittently. For example, the pattern of cloudiness and rainfall failed to show an El Niño-like pattern until early February, and even then the response was short-lived. This indicator is important because above average rainfall in the vicinity of the international dateline is considered essential in triggering El Niño’s global climate impacts. Recently, temperatures below the surface of the tropical Pacific have increased in response to a weakening of the trade winds. This excess subsurface heat has the potential to further warm the tropical Pacific sea surface in the coming several months. On the other hand, March and April are usually months of dissipation of El Niño and La Niña episodes, decreasing the likelihood of El Niño ocean conditions emerging during these months.
The latest outlooks from climate models and expert opinion suggest approximately equal chances for either warm-neutral or weak El Niño ocean conditions from March through May 2015. Toward the middle of the year, a majority of models suggest El Niño conditions, while some models predict only warm-neutral tropical Pacific sea surface temperatures. It is important to note that longer range forecasts made during the first quarter are known to have lower skill than forecasts made at other times of year, as the Pacific ocean-atmosphere system is in a markedly fluid state between April and June. Hence, outlooks tend to have a higher degree of spread at this time, suggesting 2015 outcomes could range from neutral to strong El Niño conditions. As a result, while current forecasts imply that a careful watch must be kept on the tropical Pacific Ocean temperatures, it is too early to assess the strength of any potential event.
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. For example, the state of the Indian Ocean Dipole, or the Tropical Atlantic SST Dipole, may impact the climate in the adjacent land areas. Locally applicable information is available via 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).
The situation in the tropical Pacific and Indian Ocean 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 the National Meteorological and Hydrological Services. For web links of the National Meteorological Hydrological Services, please visit:
For information on WMO Regional Climate Centres (RCCs) and links please visit:
External Links for more information
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