Playing Hide and Seek with El Niño

Abstract:

The year 2014 started out with a bang when a series of westerly wind bursts occurred west of the date line between January and April. These wind bursts generated a series of powerful downwelling Kelvin waves that led to anomalous warming in the equatorial cold tongue of the eastern Pacific, apparently signaling the onset of an El Niño. The Kelvin waves observed in February through April 2014 were as large as those seen at the onset of the 1997-98 El Niño, the strongest on record, leading to speculation that a major event was underway. Moreover, there was broad consensus among forecast models for development of an El Niño during the second half of 2014. Thus, the scientific community and the popular press were abuzz with the prospect of climate fireworks reminiscent of 1997-98. However, the atmosphere did not immediately respond to the initial oceanic warming and the positive ocean-atmosphere feedbacks that characterize El Niño evolution did not materialize. By the end of 2014, only weak warm sea surface temperature anomalies were evident in the tropical Pacific, and those anomalies were predicted to dissipate in boreal spring of 2015. Instead of fading though, El Niño came roaring back with renewed vigor in 2015. This presentation will describe the surprising evolution of conditions in the tropical Pacific during 2014-15, how forecasts and conventional wisdom failed to anticipate what occurred, and what the implications are for future research on El Niño.