The National Oceanic and Atmospheric Administration (NOAA) says La Nina continued to weaken during February and ENSO-neutral conditions are expected to return between March and May and continue through the summer.
"The rapid weakening of the negative surface and subsurface temperature anomalies during February 2012, combined with the historical tendency for La Nina to dissipate during the Northern Hemisphere spring, lends support to the return of ENSO-neutral conditions in the coming months," says NOAA. "Therefore, La Nina is expected to transition to ENSO-neutral conditions by the end of April 2012."
Still, NOAA says because impacts often lag the demise of an ENSO episode, La Nina-like impacts are expected to persist into the upcoming season. "Over the U.S. during March-May 2012, La Nina is associated with an increased chance of above-average temperatures across the south-central U.S., and below-average temperatures in the northwestern U.S.," it predicts. "Also, above-average precipitation is favored across western Washington, the Ohio Valley and lower Great Lakes, while drier-than-average conditions are more likely across Florida, the Gulf Coast and the southwestern U.S."
Juli says: When La Nina ends is very important. After La Nina ends, it still impacts the atmosphere for around a month. Therefore, the sooner La Nina ends, the sooner weather will return to "normal."