The 'European's' Joaquin forecast was better
For anyone living or owning property on the East Coast, the message was ominous. "A significant adjustment to the forecast has been made this afternoon," the National Hurricane Center reported in its 5 p.m. Wednesday Hurricane Joaquin update, "and this shows an increased threat to the mid-Atlantic states and the Carolinas."
For anyone living or owning property on the East Coast, the message was ominous.
"A significant adjustment to the forecast has been made this afternoon," the National Hurricane Center reported in its 5 p.m. Wednesday Hurricane Joaquin update, "and this shows an increased threat to the mid-Atlantic states and the Carolinas."
Then came the caveat: "However, confidence in the details of the forecast . . . remains low, since we have one normally excellent model that keeps Joaquin far away from the U.S. East Coast."
The computer model in question was the one run by the European Center for Medium-range Weather Forecasting, better known as simply the "European."
Three years ago, the European was the first to predict that Sandy would make a counterintuitive left turn before making landfall. And it did.
Last week, the European again got it right.
Any serious meteorologist is quick to point out that forecasting the behavior of the atmosphere offers infinite opportunities for lessons in humility.
Alan Thorpe, director general of the European Center, is on board with that notion. In a phone interview Monday from Reading, England, he was not about to claim victory over his New World counterparts.
"Some forecasts are much less successful," he said. "Even ECMWF's."
For example, in late January, the European had Philadelphia buried under 30 inches of snow. What followed was a forecast so bad that the local National Weather Service chief apologized for it.
"No single model is correct 100 percent of the time," said William Lapenta, director of the weather service's National Centers for Environmental Prediction. That's why the hurricane center's forecasts take into account multiple models and forecaster experience, he said.
Like every model, the European is wholly dependent on the worldwide measurements that constitute the "initial condition."
Using the laws of physics, models then try to calculate how conditions will change in the next six hours, 12 hours, 18 hours, and so on. The more imperfect the initial conditions are depicted, the worse the model runs will be.
The atmosphere is a three-dimensional fluid, 10 miles deep, sloshing on a surface spinning at 1,000 m.p.h. that is hurtling through space, and it doesn't stand still for analysis.
Satellites have improved measurements, but the gaps are so significant that forecast centers run "ensembles" that try to account for different possibilities. The European runs 52 of them.
Thorpe said that in the case of Joaquin, early last week the ensembles had the storm crashing into the United States.
"We had a very low level of confidence," he said.
By midweek, that had changed. "On Wednesday, more and more ensemble members were going out over the Atlantic."
Twelve hours later, however, the hurricane center was backtracking. By 5 a.m. Thursday, the storm was taking a track parallel to the Jersey coast, and subsequent runs carried it farther out to sea.
Thorpe said the key to knowing where a hurricane is going is to understand what is happening with the neighboring weather systems that are steering it.
Getting a handle on those is all about getting that initial condition.
"The EURO 'initializes' the atmosphere better," NBC10 meteorologist Glenn Schwartz wrote in a philly.com blog post. "There are debates about the reason why, but not about this basic fact. If we use the EURO to initialize, the U.S. models do much better."
But capturing the initial condition precisely remains a challenge for short-term forecasting - and for predicting what might happen in the next century, said Thorpe, adding he sees a bright future for improving observations.
"I think the prospects reducing uncertainties are very strong," he said.
International space agencies are working on the problem, and laser technology might yield breakthroughs in forecasting winds in the tropics, which are critical regions.
"We've got to understand how weather systems develop," he said. "We check that every day by making weather forecasts. . . . Our understanding will help us predict climate change better."
610-313-8210@woodt15
More Coverage
StartText
Ship with 33 people aboard sank near the Bahamas. A6.
In S.C., thousands may go days without water. A6.
Like 1962? Tallying damage from weekend nor'easter. B1.EndText