WMO: Moderate to strong La Nina to continue into 2011

October 11th, 2010 - 9:33 pm ICT by BNO News  

GENEVA (BNO NEWS) — Moderate to strong La Niña conditions are now well-established in the equatorial Pacific Ocean, and are likely to continue at least until the first quarter of next year, according to the El Niño/La Niña Update issued by the World Meteorological Organization (WMO) on Monday. These conditions may possibly further strengthen during the next 4 to 6 months.

La Niña is characterized by unusually cool ocean temperatures in the central and eastern tropical Pacific. It is the opposite of El Niño, which is characterized by unusually warm ocean temperatures.

Both events can last for 12 months or more and disrupt the normal patterns of tropical precipitation and atmospheric circulation, and have widespread impacts on climate in many parts of the world accompanied by the associated climate-related risks.

“Almost all forecast models predict continuation and possible further strengthening of this La Niña episode for the next 4-6 months, taking the event well into the first quarter of 2011,” the WMO said in a statement.

The U.N.-agency said this is because of the strong interaction between the oceanic and atmospheric aspects of the current event and the large area of below-average subsurface temperatures.

The current La Niña developed quickly in June and July 2010, following the dissipation of the 2009/2010 El Niño in April. Since August, the event has been moderate to strong.

In the central and eastern equatorial Pacific, sea surface temperatures are around 1.5 degrees Celsius cooler than average. The atmosphere across the tropical Pacific is now well coupled to this sea surface temperature pattern, with strengthened trade winds and reduced cloudiness over a substantial part of the central and eastern equatorial Pacific.

The subsurface waters of the central and eastern equatorial Pacific also strongly reflect La Niña conditions, with temperatures being 2 to 6 degrees Celsius below average. This large volume of anomalously cold water will likely maintain or strengthen the cold waters already at the ocean surface.

The WMO said the current La Niña has similarities to past events, but believes its impact upon local climates will differ from those in the past.

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