According to NOAA, El Niño has finally released its hold on the tropical Pacific after dominating the region for about a year. El Niño is the warm phase of ENSO, the planet’s single largest natural source of year-to-year variations in seasonal climate. It likely contributed to many months of record-high global ocean and air temperatures, extreme heat stress to coral reefs, drought in the Amazon, precipitation extremes in Africa, low ice cover on the Great Lakes, and more.
In April and May, El Niño weakened. Ocean surface temperatures cooled off significantly. Stronger easterly trade winds assisted in the cooling, and cooler, deeper waters began surfacing. Recent observations show surface temperatures close to average, meaning ENSO neutral conditions are now present, but it may not last long.
NOAA forecasters predict that La Niña conditions will take hold by July-September. La Niña brings cooler-than-average temperatures in the central and eastern part of the Pacific basin, strong winds at the surface and at high altitudes, and heavier rain over Indonesia.
If the prediction pans out, La Niña would be around to influence the peak of Atlantic hurricane season, meaning a potential increase in activity. La Niña is also expected to stick around through winter.
There have only been 10 times on record where ENSO flipped from El Niño to La Niña within a year. Historically, strong El Niños like we just experienced have evolved into strong La Niñas 4 out of 6 times. However, the strongest El Niño of all time led to the weakest La Niña of all time, so experts say it is hard to draw any conclusions from this small sample size when trying to figure out what we can expect later this year in regard to strength. Keep in mind though, that the strength of La Niña is not always a good predictor of the strength of the temperature or precipitation impacts in a particular place.
