Why Is Hurricane Wilma so Difficult to Track?

This is a partial transcript of "The Big Story With John Gibson," October 21, 2005, that has been edited for clarity.

JOHN GIBSON, HOST: What makes it so tough to predict Wilma's path? Let's ask Hugh Willoughby, a professor at Florida International University's International Hurricane Research Center.

So, Mr. Willoughby, you know, a lot of us have been treated, everyone has actually, over the last few days to highly contradictory predictions of where this thing is going. Why?

HUGH WILLOUGHBY, FMR. NOAA DIVISION DIRECTOR: Well, the contradiction really is on timing. They have been talking about the Fort Myers-Naples area, essentially from the start.

We run, though, a half a dozen models that we take really seriously as guidance for the forecast. And the forecasters decide which ones are most credible and essentially predict an average.

GIBSON: But, what is it that makes a hurricane go one place and not another? I mean, what's steering this thing?

WILLOUGHBY: Well, that's exactly it. They are steered by winds around the storm. And the computer models predict what the atmosphere is doing around the storm and how the hurricane moves with those winds.

What I tell my students is there is a rotating, unevenly heated fluid, that is our atmosphere, is the essence of chaos, and it's just simply hard to predict by mathematical process.

GIBSON: All right, but explain the logic here, if 140 mile-an-hour winds in this hurricane, how are those 140 mile-an-hour winds pushed and steered by winds that are much weaker?

WILLOUGHBY: Think about an eddy in a stream, the current of the stream just carries the eddy down or whirlpool in a stream, the current just carries the whirlpool downstream. That is exactly what is happening here.

GIBSON: Now, there had been some predictions that had the thing actually going quite a bit farther south than Miami, the tip of Florida, but I take it, you are not buying those.

WILLOUGHBY: Max Mayfield says don't put the skinny line in the forecast at the front of your concerns. There is a range, basically from the Keys or even south, clear up to the Tampa area and the point that everybody has been talking about is just about in the middle of that range.

And at this stage, while it is still milling over the Yucatan (search), we can't really say where the end of that rush off to the northeast is going to be.

GIBSON: You will be with the Florida International University Hurricane Research Center. Mr. Willoughby, thanks very much.

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