El Niño is officially here, and forecasters say it could grow substantially stronger in the coming months.
El Niño refers to the episodic warming of ocean temperatures in central and eastern tropical Pacific, which has ripple effects in weather systems around the globe. For example, its presence tends to decrease Atlantic hurricane activity but increase fall and winter rains in California.
Forecasting the present El Niño has proven to be a humbling experience. Last spring, the National Weather Service assigned favorable odds for its arrival by the fall, which never happened. A lack of sustained westerly winds, required to transport warm water from western to eastern tropical Pacific, was one reason.
But now that El Niño conditions are firmly established, forecasters are somewhat more confident the stage is set for intensification.
Phil Klotzbach, a climate researcher at Colorado State University who studies the effects of El Niño on Atlantic hurricane activity, points to several indicators suggesting El Niño will strengthen, and perhaps substantially.
In March, Klotzbach says, a burst of westerly winds — the strongest since 1997 — ripped across the tropical Pacific. Although a similar burst — almost as strong — occurred in the 2014, the winds did not persist. “This year’s westerly wind burst was longer-lasting and more intense than last year’s event,” Klotzbach says.
Klotzbach adds that the tropical atmosphere and ocean is much better conditioned for El Niño compared with last year. “The upper ocean heat content is higher,” he says. “This means that there is more fuel for the El Niño to develop. In addition, upper- and lower-level winds are more El Niño-like, especially when you look at the longer-term average.”
Many seasonal prediction models forecast a moderate-to-strong El Niño by the fall, supporting Klotzbach’s forecast.
El Niño conditions have flourished in recent weeks, says Paul Roundy, a professor of atmospheric sciences at the University at Albany. “Buoy observations suggest that the growth rate of El Niño conditions over the last few weeks is larger than any past event at this time of the year, even larger than the big event of 1997,” Roundy says. “The present amplitude, when compared with signals at the same time of year, for growing events, is the largest in the historical record going back to 1980.”
Roundy calls for 80 percent odds that strong El Niño conditions will develop this June and July and continue into next winter.
El Niño skeptics may recall Roundy also predicted an 80 percent chance of the development of a strong El Niño at this time last year, which proved erroneous. “I was one of those who suggested an 80 percent chance of a strong event last year,” he concedes. “Were similar patterns to develop again, I would make the same forecast. An 80 percent chance implies a 20 percent chance of failure.”
Roundy admits he could be wrong again with this year’s forecast. “The [El Niño] event could potentially fail to grow if westerly winds fail to continue to organize between now and the end of May,” Roundy says. “Should that occur, colder water would emerge in the equatorial Pacific region in June. I think the chance of such failure is 20 percent or less.”
The National Weather Service is more cautious than Roundy in its forecast.
“We have about a 70 percent probability of El Niño continuing through the summer, and then it tapers a bit into the fall” down to about 60 percent, says Michelle L’Heureux, a climate analyst at the NWS Climate Prediction Center. “The reason for these fairly modest chances is chalked up to the spring barrier in [El Niño] prediction. We recognize that this is not a good time of year to put a strong amount of faith in the models and, therefore, our probabilities and lack of commitment on future El Niño intensity reflect this.”
The National Weather Service does not make any specific forecast for the strength of El Niño in its current outlook. Other international meteorological services have also stopped short of predicting a strong El Niño.
Should a moderate-to-strong El Niño materialize as Roundy and Klotzbach predict, it wouldn’t be a bad thing in some respects. It would very likely suppress Atlantic hurricane activity this summer and fall. It could also be a boon for rain and snow in California next fall and winter, where the drought has reached historic levels.
Some other likely effects:
- Large amounts of heat from the tropical Pacific ocean would be released into the atmosphere, likely raising global temperatures to record-setting levels (note this happened last year, even without true El Niño conditions)
- Washington, D.C., might see depressed snow next winter. Washington’s two least snowy winters on record (0.1 inches at Reagan National Airport) coincided with two of the three strongest El Niño events on record (1997-1998 and 1972-1973). On the other hand, moderate El Niño events have produced some of our snowier winters, including the winter of 2009-2010.
- Link: List of El Niño impacts on North America