The La Niņa that began in June 2010 is now transitioning to neutral conditions, according to the Climate Prediction Center. Sea surface temperatures (SSTs) in the equatorial Pacific off the coast of South America are now just 0.4°C below average, the first time since June 2010 that these temperatures have not been 0.5°C or more cooler than average, the threshold for a La Niņa. However, it is possible that these water could cool a bit again over the next few weeks, so NOAA has not yet declared an official end to this La Niņa episode. Equatorial SSTs were 0.5°C below average in the central Pacific, and average to above-average temperatures have emerged in the eastern Pacific. While this signals the end to La Niņa, the CPC cautions that the atmosphere is still behaving like La Niņa is continuing. An animation of SSTs since February shows the weakening La Niņa nicely. Springtime is the most common time for a La Niņa event to end; since 1950, half of all La Niņas ended in March, April, or May.

Jeff Masters