Weather forecasters are unveiling their predictions for the winter, but there’s no consensus on exactly what mother nature will deliver.
The ever-cautious National Weather Service, which released its outlook today, predicts equal chances of a cold or mild winter in the D.C. area. But some bolder forecasters in the private sector say there is a strong signal it will be severe.
If D.C. has above normal snowfall, it would mark the fourth straight snowy winter — a stretch unsurpassed since the 1960s.
But the Weather Service outlook doesn’t help the D.C. area know what to expect. It places the D.C. area in a sprawling zone spanning the country’s midsection in which it says the climate signal is not strong enough to make a definitive call about what winter will bring.
NOAA winter temperature outlook, issued Oct. 20. (NOAA)
The Weather Service forecast is strongly influenced by its prediction that a weak La Niña event will likely develop. During La Niñas, it tends to be colder than normal in the northern United States and milder than normal in the south. Areas in between are stuck in a no man’s land, in which winter conditions could go either way or simply end up close to average.
But some forecasters in the private sector put more weight on other climate signals that the Weather Service has placed less confidence in or not emphasized. And some of these signals point in the direction of cold weather in the eastern United States.
Judah Cohen, a meteorologist at the private firm Atmospheric Environmental Research, has established a strong track record by using a model that predicts the phase of the Arctic Oscillation. Winters in which the Arctic Oscillation is negative tend to be cold and snowy in the eastern United States. Big areas of “blocking” high pressure develop at high latitudes, which force cold air from the Arctic south.
Cohen’s research has shown Eurasian snow cover during October is a key predictor of the winter Arctic Oscillation. When snow cover builds up quickly in this region during fall, it is a strong indicator that the winter Arctic Oscillation will average negative, he said.
“Eurasian Snow cover is quite a bit above normal this year so far,” Cohen said. “The signals are strong right now for a cold winter in the East.”
Cohen published his preliminary temperature outlook on Wednesday, which shows deep blues from the Northern Plains to the Mid-Atlantic signifying cold.
Judah Cohen preliminary winter temperature outlook. (Judah Cohen via the National Science Foundation)
While Cohen said current signals suggest severe winter weather in the East, he cautioned the outlook is tentative. “It’s still pretty early, so I can’t rate confidence very high,” he said.
Although there are meteorologists who swear by Cohen’s methods, others are skeptical or even dismissive.
For years, the Weather Service has resisted incorporating Cohen’s methods into their outlook. “Some of [Cohen’s] mechanisms seem a little bit challenged and don’t meet the statistical significance we’re looking for,” said Mike Halpert, director of the Weather Service’s Climate Prediction Center, on a conference call with reporters. “[Eurasian snow cover] contributes some degree of variance but not enough to be actionable in our forecast.”
A look back at 5 of the worst snowstorms to hit D.C. Embed Share Play Video1:29
D.C. has earned a reputation for freaking out about snow. But these five snowstorms proved to be worthy of the frenzy they caused. (Claritza Jimenez/The Washington Post)
Several other forecasters in private industry have issued cold and snowy winter predictions consistent with Cohen’s — although they rely on slightly different methodologies.
Matt Rogers, president of the Commodity Weather Group, said his company favors a cold winter based on the combination of La Niña and warmer-than-normal ocean waters in the northeast Pacific Ocean, sometimes referred to as the “blob.” The “blob” was present during the cold winters of 2013-2014 and 2014-2015, and favors a bulge in the jet stream over the West Coast and a downstream dip in the East — which promotes the delivery of cold air.
Sea surface temperature difference from normal in the Northeast Pacific Ocean. (NOAA)
“I think that the buildup of warm ocean water temperatures anomalies in the Gulf Alaska and the Bering Sea is significant and could have a major impact on the overall winter pattern just like it did in 2013-14,” says Dave Tolleris, a meteorologist who runs the consulting firm WxRisk. Tolleris leans toward a cold, snowy winter in D.C but cautions the ocean temperature pattern in this region could change which would affect his outlook.
The warm northeastern Pacific Ocean waters have also been a key factor in the winter outlook of Joe Bastardi, of WeatherBell Analytics. Bastardi has called for a cold and snowy winter in the East since July and predicts snowfall 120-150 percent of average in D.C. He also notes the Arctic Oscillation is strongly negative right now, which often carries over to winter and supports Cohen’s ideas.
AccuWeather and the Weather Company (Weather.com) seem to occupy a middle ground, neither as equivocal about cold and snow as the Weather Service nor as gung-ho as some other forecasters.
AccuWeather’s outlook calls for above normal snow in the Northeast United States, but less in the Mid-Atlantic. “[A]ccumulation may be limited in areas south of New York City, such as Philadelphia, D.C. and Baltimore,” its outlook says. “These areas will see a handful of changeover systems, where falling snow transitions to rain and sleet.”
The Weather Company is calling for warmer-than-normal temperatures over the entire country, except for New England, largely based on climate model forecasts.
Interestingly, though, when the Weather Company examined past winters in which the weather pattern best resembles the one upcoming, the winter of 1995-1996 emerged. In the D.C. area, this ranked as one of the snowiest on record. That winter featured a weak La Niña and a strongly negative Arctic Oscillation which spurred frequent “blocking” patterns and cold air delivery.
While Cohen’s outlook would favor such “blocking,” Todd Crawford, the Weather Company’s chief meteorologist, isn’t yet buying in. “I’m not seeing anything that’s getting me too excited about a big blocky type of winter yet,” he said in an email.
Tolleris is also unsure about how the Arctic Oscillation will evolve. “Over the last few winters the buildup of impressive snow cover in October in Siberia has not translated into a prolonged negative Arctic Oscillation and blocking patterns,” he said.
Winter outlooks, in general, should be considered low confidence endeavors. The science which inform them is not mature, and it’s debatable whether they have meaningful practical value for decision-making.
The Capital Weather Gang will issue its own winter outlook in early November, but we will again emphasize such outlooks are low confidence and should be taken with a gain salt.