Here's Why the 'Historic Blizzard' Weather Forecast Was Wrong
As 2015's great blizzard fizzled into not much more than a moderate snowstorm, people started asking what went wrong.
The predictions proved to be off wildly. While as much as 30 inches of snow was predicted, the five boroughs received an average of just 9.2 inches (Queens saw the most, with 12.1).
Even before the storm, people were talking about European versus U.S. weather prediction systems and the relative strengths of each. While U.S. services were predicting a smaller storm (correctly, as it turned out), many commentators were giving priority to the European predictions. And for good reason. Since the Eighties, explains Kerry Emanuel, a professor of atmospheric science at the Massachusetts Institute of Technology, the European model has generally been regarded as the better system.
"What you find is that, on average, the European model demonstrates more skill than the American model," Emanuel tells the Voice. "It's been widely known for years that the Europeans outgun us."
It's just that this time, the Europeans got it wrong. And the whole (meteorology) world was listening.
As with everything in weather prediction, the reasons behind the precision of the European model are complex, Emanuel says. But it helps to understand exactly what's going on when meteorologists do their work. Both the U.K.-based European Centre for Medium-Range Weather Forecasts and the National Centers for Environmental Prediction, its U.S. counterpart, use computer models to try to estimate how weather events will play out.
The supercomputers that do the job are fed by a huge system of actual, physical measurement sources — there are planes measuring air pressure and buoys measuring wave height and weather balloons posted up at high altitudes. All of that raw data is used to virtually re-create the actual conditions and see what will happen next.
But as Emanuel explains, it's always an imperfect system, because we can't measure every part of the atmosphere all the time. And even if we could, that data still has to be interpreted. Things get a bit tricky in that gap between what's actually happening and where things are headed. In a big, complex weather system, every misleading bit of data or anomalous reading can multiply and "spoil the forecast," Emanuel says.
The European model has proven better at getting from raw data to reliable prediction. One reason for this will surprise no one — the Europeans have been investing in their infrastructure, while cuts in funding on this side of the pond have led to an underfunded system. Originally it was a matter of simple computing power, Emanuel says. For years the advanced computers in the U.S. just weren't a match for those used by the Europeans. But that imbalance has been largely corrected more recently. But another reason, Emanuel says, is that the responsibilities shouldered by the NCEP are considerably more onerous than those handled by the ECMWF. The U.S. has a much larger and more complex weather system, and the NCEP is tasked with modeling not just nationally, but regionally.
But Emanuel says it's also about politics, and American legislators don't always see the value in investment in this kind of technology. The issue came up after Hurricane Sandy, when the European model correctly predicted the site and time of the storm's landfall, making preparation easy. The American model during that storm didn't fare as well, prompting calls for securing better funding and bringing the American system up to par. But those calls went nowhere. One commentator noted at the time, with breathtaking ignorance, that we didn't need to invest in weather prediction, because we have the Weather Channel. (The Weather Channel, of course, gets its data from these sources.)
But it's not as simple as tossing out the American model and pledging fealty to the European weather soothsayers, Emanuel says. Combining the two models is always better, because two separate predictions will always offer a better result than just one. And in this storm, the European model actually fell flat.
Any time there's a failed prediction, the public tends to throw up its hands in disgust. But Emanuel says people tend to believe predicting the weather is more of an exact science than it really is. The inherent limitations are something the meteorological community hasn't done a great job of conveying, he says. This storm, for example, was simply an unpredictable one. But that unpredictability is, in fact, predictable.
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"We're not just making a forecast, we're making a forecast of the uncertainty of the forecast...you get a cloud of probabilities rather than a spot," Emanuel says.
"For [yesterday's expected blizzard], we knew that the forecast wasn't going to be very good," Emanuel says. "The models didn't agree with each other very well." That's in contrast with Hurricane Sandy, when "all the models pretty much agreed." But that fact got lost in the coverage, partly, Emanuel says, because meteorologists don't emphasize it.
As for the apparent failure of the predictions, for meteorologists, Emanuel says, the ire of the public comes with the territory. In the ancient world, prophets played a dual role, Emanuel notes: They were supposed to see the future and tell the people what it held, but they were also supposed to serve as the official takers of blame when things went wrong, or when events didn't turn out as foretold.
Last night, Gary Szatkowski, a meteorologist with the National Weather Service in Mount Holly, New Jersey, tweeted an apology for the poor predictions.
My deepest apologies to many key decision makers and so many members of the general public.
— Gary Szatkowski (@GarySzatkowski) January 27, 2015
You made a lot of tough decisions expecting us to get it right, and we didn't. Once again, I'm sorry.
— Gary Szatkowski (@GarySzatkowski) January 27, 2015
For once, the internet was reasonable, and most replied with messages of support. But Emanuel says Szatkowski was doing what those who try to see the future have always done.
"Even though I could defend them, and I could defend their forecast, good forecasters take the blame on themselves," Emanuel says. "It's the opposite of what a politician would do. They take it on their shoulders partly for the politicians' benefit."
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