Reading the Snowflakes, Judah Cohen ’85 Calls the Weather
Judah Cohen ’85, GSAS ’94 saw the return of the polar vortex before anyone else. Months before repeated snowstorms hit New York and Boston in 2014, he warned that the northeastern United States was in for an “active and interesting” winter. A commercial weather and climate analyst in Boston, Cohen has called three of the last four winters correctly, and his long-range forecasts have hit the mark 75 percent of the time, an astoundingly good record in a field notorious for its bad calls.
“It’s incredibly satisfying to be right,” he says. “It almost feels like having super powers.”
COURTESY JUDAH COHEN ’85, GSAS’94
Cohen’s approach is unique. In mid-November, he looks at how much snow accumulated in Siberia the month before to predict how cold and snowy the eastern United States and Europe will be come January. By contrast, most of his peers look south to the tropics and use dynamical models to predict how the El NiñoSouthern Oscillation (ENSO) and other dominant climate patterns will evolve. Cohen’s outlooks often best the National Oceanic and Atmospheric Administration and other government agencies.
“He’s a master at sensing and feeling out special patterns, especially this one,” says his former Ph.D. adviser, David Rind GSAS’76, an emeritus researcher at the NASA Goddard Institute for Space Studies (GISS).
As Cohen explains it, when snow cover in Siberia is heavier than usual, a dome of cold and dense air forms over the ground, forcing the jet stream north and sending strong atmospheric waves high into the stratosphere. The polar vortex breaks down, spilling frigid air over the Arctic into North America and westward into Europe.
Though his hypothesis has yet to be fully validated by dynamical models — considered the bible of modern forecasting — the media has embraced it. “Judah Cohen’s winter forecasts have a stellar track record,” says Jason Samenow, weather editor for The Washington Post. “His methodologies, while still needing to stand the test of time, show tremendous promise.”
Cohen grew up with his eyes on the weather. At the ocean’s edge, in Sheepshead Bay, Brooklyn, he noticed thunderstorms were more common and coastal storms often brought more snow than to other parts of New York City. The eldest son of an ice cream distributor and computer programmer, he arrived at Columbia knowing he wanted to study the weather.
Though Columbia did not offer meteorology classes, it did provide access to some of the best minds in climate science, at GISS. Located above Tom’s Restaurant, where it remains, GISS ran its climate models on an IBM computer that filled an entire floor. Cohen shared an office with two other work-study students.
After graduating with a degree in geology, he set out for the University of Washington and a Ph.D. in meteorology but left after one semester. He wasn’t interested in his assigned master’s topic, fog in the Los Angeles basin. Snow was his passion. Back at Columbia, on his way toward a Ph.D. in atmospheric science, he first noticed that snow created problems when inserted into climate prediction models. Thick or thin, snow cover seemed to have no effect on the predicted weather.
"It's incredibly satisfying to be right. It almost feels like having super powers."
To anyone familiar with real-world weather, including the professors evaluating Cohen’s master’s thesis, this seemed absurd. Splitting with his advisers at GISS, the observational scientists at Lamont-Doherty Earth Observatory flunked him. Mark Cane, the Lamont scientist who built the first model predicting an El Niño event, was called in to break the tie. “It was like the Roman Colosseum,” Cohen remembers. “Cane was going to decide — thumbs up or thumbs down.”
Spared from the lions that day, Cohen vowed to work harder and question the models. “It bred in him a need to rely more on observations,” says Rind.
On a cold day in December 1994, Cohen passed his Ph.D. defense, a mug of snow by his side for good luck. He was married by then to Sherri Rabinovitz BC’91, a psychology major he met on the bus ride home from a Washington, D.C., rally to support Jews trying to flee the Soviet Union. They moved to Boston, and Cohen started a postdoctoral fellowship at MIT.
At the encouragement of his adviser, he added snow cover on land to his climate models and came to favor Arctic snow over ENSO as the lead predictor of winter weather. “It was complete blasphemy,” he says. “I’d go on job interviews and people would lecture me on how wrong I was.”
Atmospheric and Environmental Research, a commercial weather firm in Lexington, Mass., hired him as a staff scientist in 1998 and promoted him to director of seasonal forecasting seven years later. Now living in Newton, he and his wife have a daughter, Gabriella BC’18, and twin 17-year old sons, Jordan and Jonathon.
After a string of snowy winters, Cohen in late December 2010 penned an Op-Ed in The New York Times, “Bundle Up, It’s Global Warming.” He explained that the extreme cold in the United States and Europe was not at odds with human-caused global warming. The rapid loss of Arctic sea ice in summer, he argued, exposed more open water to the atmosphere, with the added moisture feeding snow over Eurasia. A blizzard struck New York that day. The phone rang steadily after.
For the last four years, Cohen has provided the winter and summer outlooks on Boston’s ABC affiliate. After his prescience last year, when Boston was buried under a winter seasonal-record 110.6 inches of snow, The Boston Globe chose to feature him and his science under the headline, “The person happiest about all this snow.”
The validation still feels sweet after what he calls “the rollercoaster” of the last 20 years. “I am very proud of all those correct forecasts,” he says.
Kim Martineau JRN’97 heads communications at Columbia’s Data Science Institute.
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