Developing El Niño Comparisons

The eastern tropical Pacific continues to warm toward a likely El Niño event later this summer that is then forecast to continue through the winter. For the first time in 3 years, the Oceanic Niño Index (ONI) has moved back into positive territory. (See

This warming is seen in all the Niño Regions with the most dramatic rise in Niño 1+2 off the South American coast where the anomalies are about +2.5 °C. 

Comparing the current event to the two previous “very strong” El Niños in late May of 1997 and 2015 shows several differences. Currently, this year has not warmed as much in the west as prior years. It also shows 2015 as more of a Central Pacific event, with more similarity between 1997 and 2023.

It will be interesting to see how the current event develops over the next six months. Stay tuned.
Jan Null, CCM
Certified Consulting Meteorologist
Golden Gate Weather Services
Twitter: @ggweather