September 9th, 2007 08:31 EST
NOAA Reports La Nina is Developing
Scientists with NOAA`s Climate Prediction Center, in today`s release of its monthly El NiÃ±o/Southern Oscillation (ENSO) Diagnostic Discussion, say that La NiÃ±a is on its way.
While we can`t officially call it a La NiÃ±a yet, we expect that this pattern will continue to develop during the next three months, meeting the NOAA definition for a La NiÃ±a event later this year, " said Mike Halpert, acting deputy director of the Climate Prediction Center in Camp Springs, Md.
La NiÃ±a refers to the periodic cooling of ocean surface temperatures in the central and east-central equatorial Pacific that occur every three to five years. NOAA declares the onset of a La NiÃ±a event when the three-month average sea-surface temperature departure exceeds -0.5 degrees Celsius (-0.9 degrees Fahrenheit) in the east-central equatorial Pacific [between 5 degrees North and 5 degrees South and 170 degrees West - 120 degrees West].
The development of La NiÃ±a conditions is supported by increasing below-normal-sea surface temperatures across the central and eastern equatorial Pacific and stronger-than-average easterly winds across the west-central equatorial Pacific. Nearly all operational dynamical models, including the National Centers for Environmental Prediction`s Climate Forecast System and many of the statistical models also favor a La NiÃ±a event, " said Halpert.
With La NiÃ±a developing, seasonal forecasters expect wetter-than-normal conditions in the Pacific Northwest and drier-than-normal conditions in the already drought-stricken southwestern U. S. this Fall.
These conditions also reinforce NOAA`s August forecast for an above normal Atlantic hurricane season, " said Gerry Bell, Ph.D., NOAA`s lead seasonal hurricane forecaster.
The Climate Prediction Center routinely publishes an assessment of ENSO conditions each Monday and the next official ENSO Diagnostic Discussion will be issued on October 11, 2007. The El NiÃ±o/Southern Oscillation Diagnostic Discussion is a product of the Climate Prediction Center in association with its funded institutions.
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