Last year, conservatives led by Rush Limbaugh called the Polar Vortex — the large-scale Arctic-air cyclone that dipped deep into American skies last year — nothing more than a “hoax” and a “left-wing media conspiracy.” Limbaugh insisted it was created for the sole purpose of frighting people into believing in climate change. Meteorologists and other scientists retaliated, insisting the phenomenon was, indeed, real. NBC weatherman Al Roker got the last word in this public spat when he posted a page from a 1959 college textbook on Twitter that contained the term and its definition. Limbaugh was uncharacteristically silenced.
This year, however, the debate isn’t about the vortex’s existence, it’s between the two commercial forecasting networks, AccuWeather and the Weather Channel, and the National Oceanic and Atmospheric Administration’s Climate Prediction Center. The commercial forecasters are telling us to brace for the return of the Arctic air in the U.S. while the federal forecasters have countered by saying another wavy vortex dipping far south is “unlikely.”
Some climate scientists we talked to said they're particularly curious about AccuWeather's methodology, considering that it's quite a daring prediction. And while meteorologist Eric Holthaus, writing for Slate, points out that AccuWeather (along with the Weather Channel) does not make its verification data available for review, he assures us that, “these folks are not the Farmer’s Almanac. There’s some science at work here.”
So, is AccuWeather the Fox News of meteorology or not? It has recently drawn fire for other ambitious long-term forecasts, with some critics calling them notably inaccurate. Last year, meteorologist Jason Samenow, the weather editor for the Washington Post, called AccuWeather's new 45-day forecasts "a joke" and "not rooted in science." He says AccuWeather "is simply peddling a useless product to people who don’t know better."
Earlier this month, AccuWeather released an audacious long-term forecast, covering the meteorological winter (December through February) in the U.S. With some certainty, it wrote:
Cold air will surge into the Northeast in late November, but the brunt of the season will hold off until January and February. The polar vortex, the culprit responsible for several days of below-zero temperatures last year, will slip down into the region from time to time, delivering blasts of arctic air.
AccuWeather also sees higher than usual snow accumulation, especially for the Northeast, and cold temperatures, ice and a few wintry blasts for the South. However, its long-range forecaster, Paul Pastelok, assures us that “it’s not going to be the same type of situation as we saw last year, not as persistent.”
Compared to AccuWeather, the Weather Channel's forecasts are a bit more conservative. The Atlanta-based company typically only issues regional temperature outlooks, instead of focusing on precipitation and weather patterns like its competitor. The Weather Channel's winter forecast is guessing that the winter's chill will be more focused on the Northeast. The meteorological media network cites research that links the size of Siberian snowpacks in October to with frigid conditions impacting the U.S. in the winter. Theoretically, when the Siberian snow advances rapidly, it favors a negative phase of the Arctic Oscillation, which is often associated with colder than average weather in the Eastern U.S. Notably, points out the Weather Channel, the snowpack in Siberia is accumulating greater than it was last year at this time.
Capping off this month’s string of predictions, NOAA’s Climate Prediction Center countered with its own forecast, saying its probable that the upcoming winter months will not be nearly as cold and unpleasant as last year, and persistent, large-scale atmospheric climate patterns are “really unlikely to form.” They’re calling for a weak El Niño to form toward the end of 2014, which makes incursions of cold Arctic air less likely. But as usual, the federal weather service is non-committal when it comes to winter weather in the Northeast, only indicating that there will likely be more precipitation than usual. Overall, it will be a pretty average winter without a lot of extreme conditions, says Mike Halpert, the acting director of the Climate Prediction Center.
Halpert says drawing a link between the Siberian snowpack and harsh winter weather in the U.S. is a compelling theory, but it's still relatively new. NOAA would need to see more years of data to determine if it's an accurate forecasting tool.
So, which forecast should we believe?
“The NOAA forecast is truer to the science in that it is stated in terms of probabilities, and does not express a high degree of confidence in any one outcome,” says Prof. Adam Sobel, of Columbia University’s Department of Applied Physics and Applied Mathematics. “That doesn't mean it won't be a cold winter, as AccuWeather says; it might be. It just means there is no way of being anywhere near as certain as their forecast implies.”
Sobel, the author of Storm Surge, a book about Hurricane Sandy and its relation to climate change, wonders if AccuWeather is taking its cue from the way daily weather forecasts are reported. He says that those, too, should be stated in terms of probabilities, but consumers seem more comfortable with deterministic forecasts where temperatures, precipitation amounts, wind speed and other measurements are predicted. So, this may be why AccuWeather and other weather news outlets choose to provide deterministic seasonal forecasts.
“I think that is unwise, given the low skill of seasonal forecasts in particular,” says Sobel. “It gives the public the wrong idea about the nature of the information they are being given. I believe most people are capable of understanding basic probabilities, and would be better served by forecasts stated in those terms.”
Sobel says that AccuWeather undoubtedly has access to most or all the same information as NOAA, but may be interpreting it differently.
“But I think it would be misleading to focus on this difference,” he says. “The more important point is that both forecasts are uncertain, and should rightly be expressed in terms of slight changes in the probabilities. NOAA does express it this way, while AccuWeather doesn't.”
It should also be noted that the three seasonal forecasts aren’t so much forecasts as they are meteorological odds-making, and betting on weather on in some regions can be a high-stakes game.
“Seasonal forecasts such as these have only a modest amount of skill, even in the parts of the world where they are the best. That means if you bet on them every season for many years, you would make money in the net, but not a lot. Further, the eastern U.S. is an area where the forecasts are particularly unskillful,” says Sobel. “So a confident forecast that a cold winter — or a warm one — will occur, with no statement of uncertainty or probabilities, such as AccuWeather's, gives an exaggerated and misleading impression of the degree of certainty that is possible.”
Sobel notes that the weather in the U.S. Southwest is much easier to predict as it is more strongly influenced by El Niño events in the equatorial Pacific.
For those demanding more rigorous science behind long-term forecasts, NOAA says better seasonal predictions are coming. Halpert says that such forecasting is gradually improving due to the increased quality and quantity of data, more advanced technology and an improvement in forecasting models.
“In some ways, the improvement over time will be analogous to the improvement in weather forecasts, though at a slower pace,” says Halpert. “In the case of numerical weather prediction, at least some of the advance was due to increases in computer technology alone. In climate prediction, the science itself has to come along in addition to better computing resources.”
Sobel says that despite the headlines, it’s doubtful we will be seeing a winter as cold as last winter was in the eastern U.S.
“Last winter was very extreme by historical standards, so it is improbable in any year,” says Sobel. “No information currently available (including the state of El Niño), or that will be available ahead of time, is strong enough to change that. It's not impossible that this winter will be as cold or colder than last, it's just very unlikely.”