Transition to ENSO-Neutral Conditions Possible

Scientists at NOAA�s Climate Prediction Center are seeing signs that La Niña, a periodic cooling of ocean surface temperatures in the central and east-central equatorial Pacific Ocean that influences U.S. weather patterns, could soon be coming to an end.

In the latest ENSO Diagnostics Discussion released on May 8, NOAA forecasters� state La Niña continued to weaken in April 2008, and predict a transition to neutral conditions is possible during June or July.

Currently, ocean temperatures remain below normal, but are approaching near-normal state. Also, many computer models indicate this trend will likely continue. La Niña episodes often dissipate over the spring and early summer.

La Niña developed during July through September 2007, and became strong during December 2007 through February 2008. Throughout the winter, La Niña was associated with very heavy precipitation in the Ohio Valley and in the northern Rockies, and generally drier-than-average conditions over parts of the southern Plains and the Southeast.

Typically, La Niña does not have strong impacts for the United States within the spring and early summer. However, this episode will need to be closely monitored since La Niña can influence the hurricane season in late summer and fall. NOAA will issue its North Atlantic, central Pacific and eastern Pacific hurricane outlooks in late May.

Relevant Websites

ENSO Diagnostic Discussion and Weekly Update
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.shtml

ENSO FAQs
http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/prelude_to_ensofaq.shtml

El Nino/La Nina Web Page
http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/enso.shtml

Behind the Scenes
http://www.magazine.noaa.gov/stories/mag229.htm