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RE: La Nina
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La Nina, a weather phenomenon usually linked to heavy rains and flooding in Asia-Pacific and South America and drought in Africa, seems to have reached its peak and is expected to fade between March and May, the World Meteorological Organization (WMO) said on Friday.
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A Growing La Nina Chills Out the Pacific

The tropical Pacific Ocean has transitioned from last winter's El Niño conditions to a cool La Niña, as shown by new data about sea surface heights, collected by the U.S-French Ocean Surface Topography Mission (OSTM)/Jason-2 oceanography satellite.
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El Niño
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Link Between 1918 El Niño And Flu Pandemic
Research conducted at Texas A&M University casts doubts on the notion that El Niño has been getting stronger because of global warming and raises interesting questions about the relationship between El Niño and a severe flu pandemic 91 years ago. The findings are based on analysis of the 1918 El Niño, which the new research shows to be one of the strongest of the 20th century.
El Niño occurs when unusually warm surface waters form over vast stretches of the eastern Pacific Ocean and can affect weather systems worldwide. Using advanced computer models, Benjamin Giese, a professor of oceanography who specialises in ocean modelling, and his co-authors conducted a simulation of the global oceans for the first half of the 20th century and they find that, in contrast with prior descriptions, the 1918-19 El Niño was one of the strongest of the century.

Source: Texas A&M University

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New Type of El Niño Could Mean More Hurricanes Make Landfall
El Niño years typically result in fewer hurricanes forming in the Atlantic Ocean. But a new study suggests that the form of El Niño may be changing potentially causing not only a greater number of hurricanes than in average years, but also a greater chance of hurricanes making landfall, according to climatologists at the Georgia Institute of Technology. The study appears in the July 3, 2009, edition of the journal Science.

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RE: La Nina
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2009 is expected to be one of the top-five warmest years on record, despite continued cooling of huge areas of the tropical Pacific Ocean, a phenomenon known as La Niña.
According to climate scientists at the Met Office and the University of East Anglia the global temperature is forecast to be more than 0.4 °C above the long-term average. This would make 2009 warmer than the year just gone and the warmest since 2005.
During La Niña, cold waters rise to the surface to cool the ocean and land surface temperatures. The 2009 forecast includes an updated decadal forecast using a Met Office climate model. This indicates a rapid return of global temperature to the long-term warming trend, with an increasing probability of record temperatures after 2009.

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Scientists with NOAAs Climate Prediction Centre, in todays release of its monthly El Niño/Southern Oscillation (ENSO) Diagnostic Discussion, say that La Niña is on its way.

While we cant officially call it a La Niña yet, we expect that this pattern will continue to develop during the next three months, meeting the NOAA definition for a La Niña event later this year - Mike Halpert, acting deputy director of the Climate Prediction Centre in Camp Springs, Md.

La Niña refers to the periodic cooling of ocean surface temperatures in the central and east-central equatorial Pacific that occur every three to five years. La Niña originally referred to a cooling of ocean waters off the coasts of Peru and Ecuador. NOAA declares the onset of a La Niña event when the three-month average sea-surface temperature departure exceeds -0.5 degrees C (-0.9 degrees F) in the east-central equatorial Pacific, between 5 degrees North and 5 degrees South latitude and 170 degrees and 120 degrees West longitude.

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-- Edited by Blobrana at 00:39, 2007-09-11

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The National Oceanic and Atmospheric Administration has predicted that La Nina - a cooling of Pacific Ocean waters that generally brings a more active Atlantic hurricane season - will be absent for the next two months.
La Nina is the counterpart to the better known El Nino, a warming of Pacific waters near the equator that creates a less conducive environment for tropical cyclones in the Atlantic. Both ocean conditions are hard to predict long-term and don't follow regular patterns.
This year, forecasters have predicted an above-average hurricane season, which runs June 1 through November. They believe there will be 13 to 17 named storms, with seven to 10 of them becoming hurricanes and three to five of those reaching at least Category 3 strength.

Source AP

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ESA scientists said last Friday that recent satellite measurements of a significant difference in sea-surface height between the western and eastern tropical Pacific Ocean suggest a La Nina event is beginning. El Nino's chillier sister, La Nina also is linked to wide-ranging shifts in weather patterns.

Hundreds of years ago fishermen off the west coast of Peru noted how periodically around Christmas time the waters grew unusually warm and fish became scarce: a phenomenon they called ‘the Christ Child’ - El Niño. It begins when a mass of warmer water from the western Pacific moves east, displacing cooler, nutrient-rich waters in the vicinity. This warmer water adds moisture to the atmosphere, raises rainfall levels and disrupts atmospheric circulation on a global basis.

La Niña is an equivalent cooling event during which the warm waters shift westwards to induce upwelling of cold water, reducing rainfall in the eastern equatorial Pacific but increasing it in the west. Researchers now recognise that these twin extremes of El Niño and La Niña are ocean components of a larger phenomenon that extends to the atmosphere, called the El Niño Southern Oscillation (ENSO).

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