April 2017 ENSO update: Tropical Pacific Ocean in Conflict

The tropical Pacific Ocean has been giving mixed signals recently, making a forecaster’s job even more difficult! In short, many of the computer models we use are predicting the development of El Niño over the next several months, but current conditions in the tropical Pacific aren’t showing many of the elements we’d expect ahead of a developing El Niño.

We’ve had neutral ENSO conditions since January, and forecasters predict that continued neutral is the most likely scenario through at least June. By September, chances of El Niño rise to about 50%, a slight edge over neutral (~40% chance) or La Niña (~10% chance).

What are forecasters seeing now?
We rely on prediction models because they provide the most likely evolution of the ENSO system better than we can compute on our own by eyeballing maps and charts and analyzing what has happened in the past under similar conditions.

Right now, many climate forecast models do predict the development of a full-fledged El Niño during this summer or fall. It’s likely that these models are acting on the much warmer-than-average waters near the coast of South America—the “Coastal El Niño” that I’ll get to a little bit later in this post. Predictions for the Niño3.4 region in the east-central Pacific, shown in the figure below, show chances for El Niño ramping up over the next year.