- Arctic Oscillation, more than El Nino, seen as cause of warmth
- El Nino might add to the warmth, cutting down chance of cold
The eastern U.S. has been pretty warm the past few days and is forecast to get even warmer.
That’s the kind of thing one would expect with one of the strongest El Ninos in the past 65 years under way in the Pacific Ocean. As it turns out, however, it’s probably too soon to be drawing any conclusions, and some meteorologists say there’s still plenty of time for cold.
Chances are the warmth, which could top 60 degrees Fahrenheit (15.5 Celsius) in Manhattan this weekend, is because of a weather pattern known as the Arctic Oscillation, said Mike Halpert, deputy director of the U.S. Climate Prediction Center in College Park, Maryland.
“The AO can play a significant role,” Halpert said Thursday. There has been “a positive AO since really the beginning of November, and it’s been mild across the country. It’s not something that we would attribute to just El Nino.”
The Arctic Oscillation can keep cold air penned up near the North Pole when it is positive and let the cold slip south into temperate regions when it’s negative. The pattern often operates in tandem with the North Atlantic Oscillation.
Here’s another way of looking at it: If El Nino is the happy-go-lucky nephew dancing around the living room and spilling everyone’s drinks, the Arctic Oscillation is an easily offended uncle with his little dog North Atlantic, who likes to bite.
So far, the AO has been positive and calm, along with the NAO. As long as that’s true, much of the globe’s temperate region, including the U.S., will stay warmer than normal or at least mild.
El Nino is still going strong in the Pacific and probably won’t start to weaken until 2016, the climate center said Thursday. The phenomenon is one of the top-three strongest El Ninos of all time, but the atmospheric reaction to the warm ocean water isn’t as powerful as in 1997-98, the record-holder in data going back to 1950.
At some point, El Nino, which typically means warmer weather this time of year in the Northern U.S., will probably throw its influence into this season’s mix. The two patterns together could end up making it a year without winter.
No one should count on that, though. Many meteorologists, among them Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research in Lexington, Massachusetts, think the deeper into winter we go, the more likely the AO is going to stir and go negative.
Also watching the Arctic is Todd Crawford, principal scientist at WSI in Andover, Massachusetts. When the A) goes negative, the polar vortex holding back the cold can
weaken, which can lead to “colder risks” for late winter, he said.
Cohen’s forecast calls for a blast of cold air to settle eventually across the eastern Great Lakes and into the mid-Atlantic. The scenario bears a resemblance what happened in 2010, which was also an El Nino year.
Halpert said the combination of a negative AO and an El Nino storm track that pushes moisture across the southern U.S. and up the East Coast “can be quite snowy in the East.”
In the winter of 2009-2010, when a “significant” El Nino was under way, the AO reached record levels of negativity. The result was a train of memorable snowstorms from Washington to New York.
The key here is that El Nino was weaker than the AO that year, but the results were still impressive. Washington got 56.1 inches of snow, New York had 51.4 inches and Baltimore picked up 77 inches, about 3 more than Buffalo, New York, according to the National Weather Service. Baltimore got 50 inches in February alone.
It wasn’t just the mid-Atlantic, Dallas recorded 17.1 inches of snow that winter.
So there’s still hope out there for snow lovers.
It’s all going to come down to Uncle AO’s mood.