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European model again leads the pack on Hurricane Joaquin forecast

 
This map from Thursday showed the European model's projections for Hurricane Joaquin for the next 10 days. [European Centre for Medium-Range Weather Forecasts]
This map from Thursday showed the European model's projections for Hurricane Joaquin for the next 10 days. [European Centre for Medium-Range Weather Forecasts]
Published Oct. 2, 2015

For days, the models that guide the National Hurricane Center's forecasts had been split over the future of Hurricane Joaquin.

Different models were sending the storm to Cape Hatteras in North Carolina or to Maine or to Bermuda. The official forecast — which held that the storm would make landfall in the mid-Atlantic — was "low" confidence, as the center put it. It was an attempt to compromise between models that fundamentally disagreed.

Friday, the official forecast now takes Joaquin out to sea. A direct hit on the East Coast can't yet be ruled out, but the top models doubt it.

If this forecast holds, Hurricane Joaquin will yield one clear winner: the model from the European Center for Medium-Range Weather Forecasts — or simply, the European model — which consistently forecast that Joaquin would head off to sea.

It's not the first time that the European model has led the pack. It's almost a repeat of what happened with Hurricane Sandy, but in reverse. Three years ago, the European model anticipated, far in advance, Sandy's unusual "left hook" into New Jersey. This time, the other models called for a left turn, and the European model dissented.

It's a familiar story for meteorologists who have been calling for vast and attainable improvements in American weather forecasting for years.

Over the last few decades, faster computers, superior models and new data have allowed all weather forecasting to improve, by a lot. But the United States hasn't quite matched that effort. It didn't invest in computing power and models that kept up with the potential for better forecasts.

By early 2013, the European model had nearly 10 times the raw computing capacity of the Global Forecast System, or GFS, which is run by the National Weather Service. There were other problems, too, and the cumulative effect was obvious and irrefutable: The GFS was doing worse than its rivals, and it played out in high-profile cases, like Sandy.

After Hurricane Sandy, Congress gave the National Weather Service the money for more powerful computers. In January 2015, the National Oceanic and Atmospheric Administration announced that it had increased computing capacity and begun running an upgraded model with higher resolution — a more detailed prediction.

The upgraded GFS prevailed over the European model in the blizzard that largely missed New York. Many of the forecasts confidently calling for high snow totals in New York were banking on the European model, or even outright disregarded the GFS. But despite its early victory, the upgraded GFS is still behind.

"The GFS is still quite inferior," said Cliff Mass, a professor of atmospheric sciences at the University of Washington. "We are a clear third," behind the European and British models. "Maybe they've gotten one third of the way."

Additional upgrades — which will culminate in a nearly tenfold increase in computing capacity — will help more, but simply upgrading computing capacity won't be enough to catch up. The problems run deeper, all the way down to the description and modeling of the basic physics of radiation, clouds, precipitation and turbulence, according to Mass.

Perhaps the biggest shortcoming is in data assimilation — the process of taking all of the available data and building an initial description of the atmosphere. The model runs from that, but a perfect model of the wrong atmosphere will yield a wrong answer.

"It is clear that our initializations are inferior," Mass argued. "That's the real problem. They have a lot more people and have taken a more sophisticated approach." Differences in initialization were probably at play in the different forecast for Joaquin. "There's a subtlety that the European center is getting right that we're not."

The European model's data assimilation relies on more observations than the GFS — including satellite measurements of radiation from clouds, which is crucial in areas with relatively few land observations. It also assimilates the data over time, allowing the model to start with the evolution of the weather heading into the forecast period, not just a snapshot.

The GFS is making strides in this area, but Mass says there's still a long way to go.