The disruptive La Nina weather pattern in the Pacific basin should strengthen over the next four to six months, heralding stronger monsoons and more hurricanes, the UN weather agency said. World Meteorological Organisation climate services chief Rupa Kumar Kolli said a "moderate to strong" La Nina, which appeared in July, was now well established.
Kumar Kolli told journalists that forecasts showed "rather a strengthening of this La Nina episode for the next four to six months."
La Nina is the opposition condition of the El Nino weather pattern which subsided in June after being blamed for an exceptionally snowbound winter in North America and Europe.
La Nina is characterised by unusually cool ocean temperatures in the eastern equatorial Pacific and has been associated with strong rainfall in Asia and Australia, bitter cold snaps in North America, as well as drought in South America. The WMO expert warned regions typically affected by La Nina to expect "enhanced climate change" into the first quarter of 2011, predicting a "more active than normal" monsoon. He also associated it with a more active Atlantic hurricane season.
Nonetheless, the WMO said that despite the similarity so far with previous La Nina episodes, notably with major flooding in South Asia since July, the impact of the latest one on local climates may differ from the past.
El Nino and La Nina, the complex interaction between shifting ocean currents and the atmosphere, and the broader impact beyond the Pacific remain ill understood by WMO scientists, who are also reluctant to establish clear links with climate change.
Ghassem Asrar, head of research at the WMO, noted that the number of monsoons with more intense rainfall had increased over the past 50 years.
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