blizzard of 2015

Why Snowstorms Are Still So Difficult to Predict

Humanity can rocket humans into space and vaccinate against life-threatening illnesses and kill enemies by remote control, but as you may have noticed from today’s snow totals, we still can’t accurately predict the weather. Bold forecasts, safety protocols, and a 24-hour news cycle leave little room for error, yet a slight 50-mile shift can dramatically alter a storm’s outcome. Here’s why New York’s “historic” blizzard turned out to be anything but.

The Problem With Forecasting Models
Meteorologists rely on tools like satellite, radar, and digital forecasting models to predict a storm’s path. But there are a few factors that account for model inaccuracies: According to Washington Post meteorologist Wes Junker, weather does not behave linearly, which means the models can’t just look at a weather system moving eastward and assume it will continue moving eastward. The chaotic nature of the atmosphere, combined with the fact that much of the model’s factors have to be approximated, can easily yield incorrect forecasts. Different weather services use different models, which account for discrepancies in forecasts, but even if by some miracle all of the models ended up pointing to the same weather event, there would still be a chance Mother Nature could change her mind at the last minute and prove them all wrong.

Why the Blizzard 2015 Forecast Was So Wrong
We’ll hand it off to “America’s weather boyfriend” Eric Holthaus to explain this one:

The reason for New York City’s low totals? The National Weather Service strongly weighted their forecast toward the historically more accurate European Center for Medium Range Weather Forecasting model (ECMWF) and the high resolution North American Model (NAM), which showed the Long Island snow band stalling out directly over the city. That didn’t happen. In constructing their forecast, the New York City office of the NWS all but ignored their own recently upgraded Global Forecast System (GFS) model, which showed significantly less snow in the city.

As it turns out, the heavy snowfall portion of the storm that meteorologists thought would end up in the city instead hit 50 miles east on Long Island, resulting in high snow totals there and much lower amounts in the city. Now meteorologists everywhere are forced to eat their words: