Predicting Rita

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TR: You mention the dynamics of the eye and the eyewall. How well are these dynamics understood?

AM: Hurricanes can change pretty rapidly, turn in a different direction, or go from a Category 4 to a 1. Hurricanes will go through eyewall cycles. As the new eyewalls grow and take the place of old eyewalls, we see these kinds of intensity changes. The eyewall is where you get 150-200 mph winds. Someone described Hurricane Andrew as a 30-mile wide tornado. So we want our models to incorporate eyewall dynamics correctly. We don't understand everything that causes eyewall cycles; if we are going to predict those, we want to be able to see short-term changes. If we want to learn what's causing them, we have to take more measurements. We have quite a ways to go. There are lots of things we can do to improve accuracy -- like better models not only of where the hurricane is going, but of where the storm surge is going to hit.

TR: More data and higher resolution means more computing horsepower, right?

AM: Until the last few years, weather prediction models were built for geographically large storms, like the standard low pressure systems we see on the weather maps. They did not resolve the most important weather, such as tropical storms and thunderstorms. Right now, we are testing new hurricane models, not in use yet, that run at resolutions as high as 1 to 4 km (compared with the current global models that run with 40 km grid meshes), and have much more realistic hurricane dynamics. But in order to run those we need bigger, faster computers. They should help improve the hurricane forecasts.

TR: We're trying to predict hurricanes with modeling tools meant to predict larger weather systems?

AM: We do have a model developed especially for hurricanes that is used as one of the operational ensemble models. It was developed in the early 1990s by NOAA's Geophysical Fluid Dynamics Laboratory, but it is lower resolution and does not accommodate some of the crucial physical processes. Since modeling techniques and computer speeds have advanced, we are developing a new model called the Hurricane Weather Research and Forecast model.

TR: How much computation do you have, and what do you need, exactly?

AM: The operational weather prediction system is an IBM massively parallel supercomputer in the Washington DC area, at the National Weather Service's National Center for Environmental Prediction. A weather model typically uses 500 to 1,000 processors in parallel. A faster computer is crucial, because then you can represent the real dynamics of a hurricane. To represent what is happening in the eyewall you need a very high resolution model and a very fast computer.

TR: The benefits seem obvious -- tighter predictions can save lives and avoid needless evacuations.

AM: They always used to say an evacuation alone costs a million dollars a mile. If you warn 50 miles of coastline, it's going to cost $50 million. I think that was pre-Katrina. We are going to look at Rita and Katrina and say they cost perhaps as much as $10 million per mile, and we are going to need much higher accuracy. A warning of 100 miles of coastline would cost $1 billion. There are lots of things we can do to improve our forecast so we can improve on our evacuation accuracy.

TR: What does the federal government spend on hurricane forecasting now, and what's needed?

AM: We put about $50 million total into everything from the hurricane center to the models. I think that if you really said "You know, this is an extraordinary problem that is going to cost, like Katrina did, $100 billion," you'd want to spend an additional couple hundred million a year to really improve as fast as possible.