January 26, 2011

WMO: La Nina Expected To Stick Around A Bit Longer

The La Nina weather pattern circulating through the eastern-central Pacific Ocean, which is behind the floods and extreme conditions in Australia, Asia, Africa and South America is one of the strongest ever and could last for four more months, according to the UN weather agency.

"In atmospheric terms it has to be termed one of the strongest ever La Nina episodes," Rupa Kumar Kolli, head of world climate services at the UN's World Meteorological Organization (WMO), told the AFP news agency.

"The most important impacts we have witnessed in recent months have been the devastating floods in Australia," Kolli said.

In its latest update, the WMO said that "a significant La Nina episode" was continuing in the tropical Pacific Ocean "with effects extending onto adjacent ocean basins."

All scientific outlooks show "a continuation of the current La Nina for at least the next two to four months," it added, although the climate pattern was likely to continue to weaken over that period.

Even if La Nina does weaken over the next few months, "the impacts are likely to continue," Kolli cautioned.

Besides the devastating floods in Australia and wetter-than-average weather in the western Pacific, the WMO is linking La Nina to extreme weather conditions in southern Africa, drought in east Africa and the western coasts of South America.

Deadly landslides in Brazil and flooding in Sri Lanka were also linked to Li Nina, Kolli said, even though those disasters were "atypical impacts" of the disruptive weather pattern.

The La Nina weather pattern that emerged last summer most likely combined with other local influences from the Atlantic of Indian Oceans in those instances, Kolli suggested.

La Nina by unusually cool ocean temperatures in the central and eastern tropical Pacific and typically lasts about nine months. However, the complex interaction between shifting ocean currents and the atmosphere, and its range is not fully understood by scientists, who are reluctant to establish a clear association with climate change.

The current La Nina, in terms of atmospheric effects, is ranked about the third strongest for the past century on one scale, while its cooling of Pacific Ocean waters was rated as moderate to strong, Kolli explained.


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