Press Release No. 946
For use of the information media
Continued neutral conditions also possible; Return to La Niña unlikely
Neutral conditions (neither El Niño nor La Niña) have prevailed since the 2011-12 La Niña ended in April 2012, and are likely to continue for at least the first half of the northern hemisphere summer (southern hemisphere winter). Beyond July, odds slightly favour El Niño over neutral conditions. The re-emergence of La Niña is considered very unlikely.
The Update is based on input from climate prediction centres and experts around the world and is an authoritative source of information on a phenomenon which has a widespread impact on weather and climate – and lives and livelihoods – around the globe. Scientific knowledge about El Niño/La Niña has become an important tool for policy-makers and planners in the disaster risk reduction, water management, agricultural and health sectors, to name but a few examples.
El Niño is characterized by unusually warm ocean temperatures in the central and eastern equatorial Pacific. La Niña, on the other hand, is characterized by unusually cool ocean temperatures. Both events can last for a few months and are associated with significant changes in atmospheric circulation and precipitation in various regions.
“Based largely on a build-up of heat in the deeper tropical Pacific Ocean since early May, most climate models surveyed predict development of El Niño conditions sometime during the July to September period, continuing through the rest of 2012,” said the Update.
Although many of the models that predict the development of El Niño currently indicate it will be weak, predictions of strength are not very accurate at this early stage of evolution. “Therefore, if El Niño does develop, the likely strength is considered uncertain at this time,” said the Update.
Uncertainty regarding the prospect for neutral or El Niño conditions for the second half of 2012 is due to questions about whether the expected warming of the Pacific Ocean will be large enough to cause changes in the atmosphere, which is a necessary condition to sustain an El Niño event. There should be more certainty in the longer-term outlook by August.
Past El Niño events have been associated, among others, with drought in Australia, Indonesia and in northeastern parts of South America, and with heavy rainfall in Ecuador and northern Peru. However, no two El Niño events are the same and they also vary depending on the time of the year during which the conditions evolve.
Importantly, several other factors influence seasonal climatic patterns apart from El Niño and La Niña. These include conditions in the tropical Indian and Atlantic oceans, as these can influence surrounding continental climate patterns.
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.
WMO is the United Nations' authoritative voice on weather, climate and water
For more information please contact:
e mail: cnullis(at)wmo.int
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