Long-Lasting La Niña Finally Ends

LiveScience.com Yahoo News 3 May 12;

The La Niña climate pattern that has been in place over much of the last two years finally dissipated last month as expected, and neutral conditions are now in place over the tropical Pacific, government climate scientists said today (May 3).

Officials with the National Oceanic and Atmospheric Administration had predicted in March that La Niña would peter out by the end of April.

When a La Niña pattern is in place, water temperatures in the tropical Pacific are cooler than normal, which has far-reaching consequences for climate and weather patterns around the globe.

The most recent La Niña cycle first emerged in June 2010 and had a substantial impact on the extreme winter weather of 2010-2011, as well as last spring's terrible tornado season. La Niña conditions may have helped bring about some of the massive snows that blanketed much of the northern United States last winter, but its waning may actually have been the culprit in ramping up the tornado season.

The La Niña pattern had faded out by May 2011, but re-emerged at the end of summer and gathered strength as this past winter approached.

NOAA reported today that ENSO-neutral conditions were now in place (ENSO refers to the whole La Niña-El Niño climate cycle). These conditions are expected to last through the Northern Hemisphere summer, and scientists don't expect the La Niña pattern to re-emerge later this year, according to a NOAA advisory.

Higher sea surface temperatures have emerged in parts of the tropical Pacific, but whether these warmer waters will lead to the development of a full-blown El Niño remains uncertain, the advisory noted, and the official NOAA forecast calls for equal chances of neutral conditions or an El Niño event after the summer.