The 2015–16 El Niño is in its last stages, the Australian Bureau of Meteorology (BOM) reports. Recent changes in the tropical Pacific Ocean and atmosphere, combined with current climate model outlooks, suggest the likelihood of La Niña forming later in 2016 is around 50%, meaning the Bureau's ENSO Outlook is at La Niña WATCH.
Eastern tropical Pacific sea surface temperatures have cooled significantly in the past fortnight and are now approaching neutral levels. As temperatures under the surface are below average, more surface water cooling is expected. However the atmosphere is only slowly responding to these changes, and hence, the Southern Oscillation Index (SOI) and cloudiness near the Date Line continue to fluctuate around El Niño thresholds.
According to BOM, six of eight international climate models suggest the tropical Pacific Ocean will return to neutral levels within the next month. By September, seven of eight models suggest La Niña thresholds are likely. However, individual model outlooks show a large spread between neutral and La Niña scenarios.
La Niña is characterized by unusually cold ocean temperatures in the Equatorial Pacific, compared to El Niño, which is characterized by unusually warm ocean temperatures in the Equatorial Pacific. El Niño and La Niña are opposite phases of the El Niño-Southern Oscillation (ENSO) cycle, with La Niña sometimes referred to as the cold phase of ENSO and El Niño as the warm phase of ENSO, NOAA explains.
La Niña is associated with widespread changes in weather patterns complementary to those of El Niño, but less extensive and damaging in their effects.
While models are still not in agreement when it comes to 2016/17 La Niña, research shows that strong El Niños, like the one our planet was experiencing since 2015, are more likely to transition to La Niñas. La Niña typically lasts between 10 and 12 months.
Featured image: Storm by Jussi Ollila (CC - Flickr)