The National Hurricane Center delivered an accurate forecast "56 hours before the storm came ashore, and that is astounding," Sen. David Vitter, a Louisiana Republican, said at a hearing convened by the U.S. Senate Commerce Committee's Subcommittee on Disaster Prevention and Prediction. "That's enough time to drive from New Orleans to New York, twice, with a good night's sleep both times."
A panel of witnesses at the hearing said the supercomputers that meteorologists use to model storms have come a long way over the past few decades. A greater scattering of weather buoys, which transmit observations used in the modeling, has also helped to boost accuracy.
But the computers remain too slow and don't always have a great enough density of data to make accurate predictions, said Keith Blackwell, an associate professor of meteorology at the University of Alabama's Coastal Weather Center.
"In order to speed up computer hurricane forecast simulations, (forecasters) end up taking many shortcuts on how important physical processes are calculated or represented in a model," which can "lead to significant forecast errors and often very little continuity between model forecasts," Blackwell said.
Until the modeling systems become more sophisticated, he added, "we're going to have a problem with getting people out of the way because the storm's going to do something very unexpected."
Marc Levitan, director of the Louisiana State University Hurricane Center, said his organization came up with models that predicted Hurricane Katrina's storm surge had the potential to spill water over the levies that enclose New Orleans.
But none of their models are currently capable of foreseeing the sort of levy breaches that occurred during the disaster, he said.
"Where we're lacking in the prediction sense is...predicting the human consequences," Levitan said. "What is the wind damage? What will be the number of buildings flooded, number of casualties, rescues needed?...The state of science is not there today."
Senators at the hearing nonetheless heaped praise on the forecasters' performance. Vitter said he regretted that the recovery efforts weren't equally coordinated.
"What's most frustrating is...it didn't have to be this way," he said. "There was really no element of surprise here. It wasn't just predictable, it was predicted many times over in part by these fine folks before us."