GENEVA The El Nino warming the Pacific Ocean since June has peaked, but is expected to influence climate patterns worldwide up to mid-year before dying out, the World Meteorological Organization (WMO) said on Tuesday.
However, the United Nations agency said that forecasting uncertainties meant it could not rule out the possibility that El Nino would persist beyond mid-year.
El Nino, driven by an abnormal warming of the eastern Pacific Ocean, can create havoc in weather patterns across the Asia-Pacific region, unleashing droughts in some places and heavy storms in others. It typically lasts from 9 to 12 months.
The most likely scenario is for sea surface temperatures across the tropical Pacific, which rose by 1.5 degrees Celsius at its peak last November-December, to return to normal by mid-2010, WMO said in a statement.
"El Nino is already in a decaying phase. We expect it to fully decay by mid-year and neutral conditions to be established," WMO climate expert Rupa Kumar Kolli told Reuters.
"But this is a period where the predictability of the system is very low. Things could happen very suddenly," he said.
The WMO said that the current El Nino, which can occur every two-seven years, was of a moderate level, "close to or slightly above the typical strength seen in the historical record of El Nino events."
"Even during the decaying phase of the El Nino, expected over the next few months, the conditions associated with a typical El Nino will continue to influence climatic patterns at least through the second quarter of the year," it said.
El Nino typically creates dry conditions for western areas along the Pacific Ocean such as South East Asia and Indonesia, and southern parts of western Australia, and wetter than normal conditions in western coastal areas of South America, Kolli told Reuters.
Parts of South Asia experienced drought last year due to a weak summer monsoon season linked to El Nino, and this could happen again if El Nino were to intensify in June, he said.
"That is the typical signature of El Nino," he added.
Warmer sea temperatures along some coastal regions of Latin America had caused higher rainfalls, but these were confined to relatively smaller pockets, and did not wreak havoc, he said.
The last severe El Nino in 1998 killed more than 2,000 people and caused billions of dollars in damages to crops, infrastructure and mines in Australia and Asia.
"Every El Nino is an individual event," Kolli said.
However, the phenomenon, which means "little boy" in Spanish, referring to the Christ child because it is often noticed mostly clearly in Latin America around Christmas, is also linked to a weaker than normal hurricane season in the northern Atlantic, according to the WMO expert.
The opposite cooling phenomenon, known as La Nina, or "little girl," could also start in the middle of this year, but that scenario is deemed less likely.
(To watch a Reuters Insider television's interview with WMO Chief Climate Scientist Rupa Kumar Kolli, click on the link below link.reuters.com/gyt65j )
(Editing by Jonathan Lynn)