The World Meteorological Organization says the La Niña weather event is under way across the central and eastern equatorial Pacific and these conditions are expected to continue through the first quarter of 2008. Lisa Schlein reports for VOA from Geneva the weather agency says the La Niña phenomenon can alter global weather and climate patterns.
The World Meteorological Organization (WMO) in Geneva says the sea-surface temperatures in the eastern tropical Pacific are markedly colder than normal during a La Niña. In contrast, it says El Niño events have warmer sea-surface temperatures in the same region.
WMO Senior Scientist in the World Climate Program, Leslie Malone, says the current La Niña is markedly different from most other such events in the past. This, she says, is due to the presence of colder than normal sea surface waters across northern Australia surrounding west Indonesia islands through to the Indian Ocean.
"These conditions and the changing conditions can cause unusual and sometimes severe weather events and patterns in the immediate area of the Pacific basin, but also around the world in different ways," she said. "El Niño and La Niña have a recurring pattern within a regular cycle of approximately two to seven years. But, I must reinforce that no two situations are ever exactly the same."
Because of La Niña, Malone says Indonesia, Malaysia and Northern Australia can expect much more rain during the southern summer months and the Philippines can expect heavier rainfall in the northern summer. She says dry conditions are likely to persist in many parts of Australia.
She says the devastating floods experienced between June and September in western and northern parts of the Greater Horn of Africa are also linked to La Niña. She says countries such as the Sudan, Uganda, Western Kenya, Ethiopia, Djibouti and Eritrea have been subjected to unusually heavy rain and flash floods.
"This flooding has led to crop failures, to displacement of people and to very severe human distress in the region," she added. "This is connected to both the La Niña situation that we are observing now in the Equatorial Pacific Basin and in the particular sea surface temperature conditions that we have noticed in the Indian Ocean Basin as well. These things are working in conjunction."
WMO scientist Malone says La Niña also has a tendency to increase the number of storms in the tropical Atlantic because of changing atmospheric circulation patterns in both surface and upper atmospheric levels.
She says the northwestern United States and western Canada are experiencing cooler and damper conditions than normal because of La Niña.