What is El-Niño?
El-Niño is an oscillation of the ocean-atmosphere system caused by a periodic warming of ocean temperatures in the tropical Pacific that affects weather around the world. El-Niño can cause drought in the West Pacific and rainfall in Peru and the southern United States. During a winter El-Niño episode, a strong jet stream tends to push storms south of Ohio, leaving northern states with less severe weather and milder-than-average conditions.
Source: National Oceanic and Atmospheric Administration
The good news for Ohio is the odds of next winter being as cold as last are getting slimmer.
The bad news is the cause: above-average sea surface temperatures across the eastern tropical Pacific Ocean that could wreak havoc in some parts of the world.
The conditions portend the return of El-Niño, according to scientists at the National Oceanic and Atmospheric Administration (NOAA), referring to the Spanish term used to describe the tropical warming pattern that reoccurs at different intervals.
“We can pretty safely say this. We will be warmer than last winter because last winter was so cold,” said Jamie Simpson, Storm Center 7 chief meteorologist. “And El-Niño is going to help stack the deck against a repeat of last winter.”
NOAA’s models now show a greater than 65-percent chance that El Niño will develop this year.
“The signs that we will have one developing later this year and through the winter are about as strong as we’ve had since the El Niño of ’97,” Simpson said. “That’s the last time we had a strong El Niño.”
El Niño-Southern Oscillation conditions tend to change weather patterns across the globe, cycling generally every three to five years. However, the cycle can vary from two to seven years depending on its cooling counterpart, La Niña, or neutral periods when neither is prominent.
While the warming of the ocean begins far away, the effect is felt in the weather experienced here, said Sarah Fortner, assistant professor of geology and environmental science at Wittenberg University in Springfield.
“It’s like warm water is sloshing back and forth across the Pacific. And when that warm water is sloshed up against Peru it creates this change in air masses that we feel in Ohio,” Fortner said.
The Boonshoft Museum of Discovery in Dayton has the ability, unique in Ohio, to display near real-time NOAA data sets on the museum’s Science on a Sphere. Data collected on land, water and in the atmosphere is represented visually and projected on a large globe. Past El-Niño events can be fast-forwarded and rewound to show in colored bands how ocean temperatures warm in the eastern Pacific over time and ripple across the rest of the planet.
El Niño can “mean good and bad things for weather worldwide,” said Susan Pion, vice president for education and exhibits at the Dayton Society of Natural History that operates the Boonshoft Museum of Discovery. In addition to a milder winter for the Midwest and Northeast, it could mean more precipitation for a drought-choked West. Increased wind shear, which has the ability to break up storms and keep them from becoming larger, could make for a less intense hurricane season, Pion said.
“Greater wind shear can interfere with the formation of hurricanes on the East Coast, thus possibly having a less intense hurricane season than they’ve been experiencing the last few years,” Pion said.
In part because of El Niño, NOAA predicts that the 2014 Atlantic hurricane season has a 50-percent chance of being below normal with 3 to 6 hurricanes and 1 or 2 of those becoming major.
Simpson and Fortner both said during El Niño it’s very difficult to predict which way precipitation will go in the Miami Valley — whether it comes as snow next winter or rain next spring.
During the strong 1997 El Niño, rainfall and severe storms hit the southern U.S., particularly south of the Tennessee Valley. A replay of that year could usher in a quiet spring for Ohioans in 2015, according to Simpson.
“What that does for us in terms of the severe weather season, is it has a greater tendency to push the greatest threat south of us for much of the spring,” Simpson said. “A lot of people talk about El Niño as being this horrible, horrible thing. It can actually be a positive to some. And that is one of the potential benefits we have here.”
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