UN meteorological agency reports end to El Niño pattern over the Pacific

6 July 2010 – The weather pattern known as El Niño rapidly dissipated in early May, giving way to the development of cool, neutral to weak La Niña conditions in the tropical Pacific Ocean, the United Nations World Meteorological Organization (WMO) reported today.

El Niño refers to an abnormal warming of surface ocean waters in the eastern tropical Pacific, while La Niña is characterized by unusually cool ocean temperatures in the eastern equatorial Pacific. Both events can disrupt the normal patterns of tropical precipitation and atmospheric circulation, and have widespread impacts on climate in many parts of the world.

The prevailing conditions are more likely than not to strengthen into a basin-wide La Niña over the coming months, according to the El Niño/La Niña update issued by WMO.

By mid-June, the sea-surface temperatures had decreased to approximately 0.5 degrees Celsius below normal over the central and eastern equatorial Pacific, near the borderline of La Niña conditions.

Further, below average sea temperatures exist beneath the surface of the central and eastern equatorial Pacific. Forecast models continue to predict further decreases in the central and eastern Equatorial Pacific sea-surface temperature. In particular, most dynamic models strongly favour further La Niña development, according to WMO.

While it is likely that La Niña conditions will further develop in the next several months, the timing and magnitude of such an event in 2010 are as yet uncertain, with no indications at this time of a particularly strong event in terms of sea-surface temperatures.

The unusual climate patterns and extremes that occur in association with La Niña conditions also occur independently of La Niña, and therefore individual users of climate information should seek detailed interpretation for their locations and sectors, WMO said in the update.

Over the coming months, the climate forecasting community will provide detailed interpretations of regional climate conditions through the National Meteorological and Hydrological Services, it added.

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