The collapse of El Nino in the tropical Pacific Ocean has begun and it will be rather dramatic. The current strong El Nino event reached its peak intensity level in December 2015 and all indications suggest it will completely flip to La Nina conditions by later this year. This naturally occurring oceanic cycle that produces warmer-than-normal sea surface temperatures (SSTs) in the equatorial region of the Pacific Ocean began in earnest early in 2015 and strengthened throughout the year to comparable intensity levels of the strong El Nino episodes of 1982-1983 and 1997-1998 although the warmest region relative-to-normal set up in somewhat different locations. El Nino has had widespread consequences around the world and will continue to do so in the near future. By later this year, colder-than-normal sea surface temperatures are quite likely to appear in the tropical Pacific Ocean as predicted by multiple computer forecast models and this flip to La Nina will also have extensive consequences around the world.
Rapidly changing SST anomalies
The latest sea surface temperature anomalies show noticeable changes from just one month ago across the tropical Pacific Ocean (above). Specifically, while the sea surface temperatures in that region are still above-normal, they are noticeably less so than just four weeks ago. This trend should continue over the next few months as sea surface temperatures drop off rapidly in the equatorial region of the Pacific Ocean.
Computer model forecasts suggest a dramatic flip to La Nina
Two independently-made computer forecast models depict a dramatic change in sea surface temperature anomalies in the tropical Pacific Ocean between now and late 2016. The first forecast map shown above comes from the Japan Meteorological Agency and it predicts big changes in SST anomalies between the March/April/May and September/October/November time periods. The warmer-than-normal SSTs in the tropical Pacific Ocean (red region) reverse to colder-than-normal (blue region) conditions by this fall. A second model generated by the Scripps Institute of Oceanography provides support to this flip as it also shows a dramatic change from El Nino conditions (yellow, orange) in the spring to La Nina (blue, green) conditions by the upcoming fall and winter seasons (below).
Consequences of La Nina
One of the important consequences of the current strong El Nino event in the equatorial Pacific Ocean was a spike in global temperatures. The temperature anomaly plot below (courtesy Weather Bell Analytics) shows the trend in global temperature anomalies since 2005 as measured by NOAA’s CFSR CFSv2 model. In prior El Nino events during the past decade (2006-2007, 2009-2010), there were indeed spikes in global temperatures and in each case those temperatures dropped sharply in subsequent periods after La Nina conditions became well-established in the tropical Pacific Ocean. Global temperatures may continue to stay at well above normal levels in the near term as a result of the current El Nino despite the fact that it has passed its peak intensity level as sea surface temperatures should remain above-normal for awhile. However, if recent history is any guide, expect global temperatures to drop sharply after La Nina conditions become well-established in the tropical Pacific Ocean – likely during 2017 and perhaps beyond.
Meteorologist Paul Dorian