Will El Niño Return for Summer 2017?

Rumors of El Niño returning for summer 2017 have been percolating through meteorological echo chambers for the past few months, but beginning in mid-April, mainstream media outlets like the New York Times started spilling the beans to the public at large, alerting Americans of all walks of life that another El Niño may return for the summer and persist through the winter. Indeed, climate models are in reasonable agreement that a weak-moderate El Niño will develop over the next few months. If this were to happen, it would be the most rapid switch from El Niño to La Niña and then back to El Niño since the July 1963- April 1966 time period, when we swung from El Niño to La Niña and back again over three consecutive winters, only spending a combined 6 months over that time period in Neutral, or as some prefer to call them, “La Nada” conditions.

The tropical Pacific, which can be thought as ground zero for El Niño, is currently giving us mixed signals as a whole. While the Eastern Pacific appears to be in full-on El Niño mode, the Central Pacific is still firmly in Neutral conditions, and the atmospheric circulation over the most of the tropical Pacific still looks more reminiscent of a La Niña!

Nino 3.4 SST Anomaly Predictions from a variety of different dynamical and statistical models. Taken from the Climate Prediction Center’s most recent El Nino/Southern Oscillation (ENSO) Diagnostic Discussion

For some reason, it is much harder to accurately forecast El Niño and La Niña events before spring than after spring. There are many hypothesized reasons for this – one is that spring is the time when El Niño/La Niña are decaying, and that it is easier to predict the evolution of an El Niño/La Niña when one is already underway. Evidence for this theory is supported by the fact during the springtime, dynamical models – models that predict the future state of the land, ocean, and atmosphere by plugging in a set of “initial conditions” into a given suite of equations, outperform statistical models – models that predict the future by drawing statistical correlations between the present and historical conditions. This is likely because there is a relative dearth of statistical correlation in the springtime compared to other times of the year, particularly during a time like this when the atmosphere and ocean are doing different things.

Not surprisingly, climate models show quite a bit of variance in solutions over the next several months. Still, nearly all the dynamic models show a weak-to-moderate El Niño developing, while the statistical models give us a weak El Niño or a La Nada. But most importantly, no model shows a La Niña event occurring. Given our current information, the chance for La Niña returning for next winter appears small – around 10%.

The fact that nearly all dynamical models show an El Niño developing is certainly telling, but the existence of a La Niña-esque atmospheric circulation in the Western Pacific has thus far precluded the forecasters at the Climate Prediction Center from issuing an El Niño Watch. The current probabilistic forecast has a 50% chance of El Niño conditions developing by September.

Yup, all that writing just to tell you that our state of the art climate models are just as useful as a coin flip! But hopefully you learned something along the way. El Niño conditions usually bring us warmer and slightly drier than normal weather, which I’m sure will bring a sigh of relief to many after the hectic winter and spring rains we’ve had this year!

~Charlie Phillips

Charlie Phillips, a Madrona resident, received his B.S. in atmospheric sciences from the University of Washington and works in Portland as a meteorologist forecasting wind energy along the Columbia River Gorge. Check out his weather website at weathertogether.us.