Pacific La Nina Building? La Niña may be on its way
Joshua S Hill
special to mongabay.com
September 7, 2007
Scientists with NOAA’s Climate Prediction Center are predicting that another La Niña event is on its way, according to the latest monthly El Niño/Southern Oscillation (ENSO) Diagnostic Discussion.
“While we can’t 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,” said Mike Halpert, acting deputy director of the Climate Prediction Center in Camp Springs, Md.
A La Nina event is characterized by unusually cold ocean temperatures in the eastern equatorial Pacific, compared to the El Nino effect which is marked by the reverse. In the most recent ENSO Diagnostic Discussion, released on September 6, NOAA notes that during August 2007 “negative sea surface temperature (SST) anomalies in the eastern equatorial Pacific expanded westward, and now extend from the coast of South America to the date line (180ºW)”.
According to Halpert, nearly all the operational dynamic and statistical models focusing on this effect, including the National Centers for Environmental Prediction’s Climate Forecast System, believe that a La Nina will be announced later this year.
If La Nina is announced, seasonal forecasters believe that wetter than average conditions will occur in the Pacific Northwest of America, and even drier conditions will be expected in the already drought stricken southwestern United States this coming 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.