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WMO Predicts Pacific La Nina This Year

July 7, 2010

La Nina is likely to cool the tropical Pacific waters in the months ahead, causing stronger monsoons throughout Asia and eastern Australia, according to an update released Tuesday by the World Meteorological Organization (WMO).

These conditions are also likely to promote the development of storms in the tropical Atlantic.

“Below average sea temperatures exist beneath the surface of the central and eastern equatorial Pacific, and forecast models continue to predict further decreases in the central and eastern Equatorial Pacific sea-surface temperature. In particular, most dynamical models strongly favor further La Nina development,” the WMO said in its El Nino/La Nina update.

El Nino, the opposite of La Nina and a phenomenon that warms the sea, quickly dissipated in May, leading to the current situation, the U.N. agency said.

“Following the rapid dissipation of the 2009/10 El Nino in early May 2010, a brief period of neutral conditions prevailed, leading to the current state of borderline La Nina conditions. These borderline conditions are more likely than not to strengthen to become a basin-wide La Nina episode during the second half of 2010,” the WMO said.

It is also possible, although less likely, for conditions to remain neutral throughout the remainder of the year.

“While it is likely that the La Nina conditions will further develop over the next several months, the timing and magnitude of such an event in 2010 are still uncertain,” said WMO expert Rupa Kumar Kolli during a news briefing in Switzerland.

Current conditions are not sufficient for the WMO to declare that a La Nina is actually taking place, and most of the forecasting models do not suggest a strong La Nina event in terms of sea-surface temperatures, he explained.

La Nina events are typically associated with stronger monsoons in Asia and Australia, along with an active hurricane season in the tropical Atlantic, he said.

“These are some of the risk factors that should be kept in mind.”

The top U.S. weather agency has already forecasted that the Atlantic storm season, which officially began June 1, may be the strongest since 2005.

Kolli was asked during the news briefing whether the La Nina event might threaten cleanup operations for the Gulf of Mexico oil spill.

“La Nina by itself is unlikely to play a role in that region,” he said.

Nevertheless, “considering that there is a possibility of an active hurricane season, the hurricanes definitely have the potential to churn up the sea and also play a role in the spread of the oil spill in some ways.”

“But this all depends upon the track of the hurricane and the strength of the hurricane and many other factors associated with individual hurricane events,” he said.

Kolli added that a well-established La Nina event is also associated with a small decrease in air temperature in many parts of the globe.

“That has implications for the global mean temperature,” he said in an interview with Reuters.

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