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July 7, 2010

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La Nina likely to bring storms, experts warn

LA Nina is likely to cool the tropical Pacific in coming months, a phenomenon which usually causes stronger monsoons across Asia and eastern Australia, the World Meteorological Organization said yesterday.

The weather condition also promotes the development of storms including hurricanes in the tropical Atlantic, the WMO said.

El Nino, the opposite phenomenon which warms the sea, rapidly dissipated in early May after prevailing since late 2009. This has led to the current situation, bordering on a weak La Nina event in the tropical Pacific, according to the United Nations agency.

"These borderline conditions are more likely than not to strengthen to become a basin-wide La Nina episode during the second half of 2010," WMO said in a statement.

"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," WMO expert Rupa Kumar Kolli told a news briefing in Geneva.

Current conditions are not adequate for the WMO to declare that a La Nina event is actually in place, he said. It is possible, but less likely, for neutral temperatures to prevail for the rest of the year.

Most forecasting models do not indicate a particularly strong La Nina event in terms of sea-surface temperatures, he said.

Typical La Nina events are usually associated with stronger monsoons in South Asia, Southeast Asia, parts of East Asia and also Australia. A La Nina event is also associated with an active hurricane season in the tropical Atlantic, Kolli said.

"So these are some of the risk factors that should be kept in mind," he said.

The US government's top weather agency has already predicted that the Atlantic storm season which began on June 1 may be the most intense since 2005 when Hurricane Katrina killed more than 1,000 people and disrupted oil production by crashing through Gulf of Mexico energy facilities.

Kolli, asked about the possible effects of La Nina on efforts to clean up BP's Gulf of Mexico oil slick, said: "La Nina by itself is unlikely to play a role in that region.

"But 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."

Changes in sea temperatures in the Pacific are strongly linked to major climate fluctuations around the globe, and once underway such events can last 12 months or more, according to the WMO. A strong El Nino event of 1997-98 was followed by a prolonged La Nina phase from mid-1998 to early 2001.

If a La Nina event becomes well-established, it is also associated with a slight decrease in air temperature in many parts of the world, according to Kolli.



 

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