Hurricane Forecaster Offers Insight On Storms
MICHELE NORRIS, host:
The art of forecasting hurricanes has evolved a lot over the past few decades. Still, as Hurricane Gustav showed, forecasters have a hard time predicting how strong a storm will be when it hits, and when it will actually hit.
Joining us to talk about that is Christopher Landsea. He's the science and operations officer at the National Hurricane Center in Miami. Welcome to the program.
Mr. CHRISTOPHER LANDSEA (Science and Operations Officer, National Hurricane Center): Good afternoon. How are you doing?
NORRIS: First of all, let's talk briefly about Hurricane Gustav. What did forecasters get right in that case, and what did they get wrong?
Mr. LANDSEA: The track predictions came out exceptionally well. Even out four and five days in advance, we were thinking about the central north Gulf Coast, in Louisiana, and that's where it ended up happening. So track-wise, we did a very good job on that one.
NORRIS: And what did they perhaps get wrong?
Mr. LANDSEA: Well, unfortunately, the wind-speed forecasts were not nearly as good. Early projections were that it was going to be coming ashore as perhaps a Category 4 hurricane, and it ended up - instead of re-intensifying over the Gulf of Mexico after it hit Cuba, it weakened, and it came ashore as a high-end Category 2. Very good news for Louisiana, but it kind of highlights our limitations in issuing skillful wind speed forecasts.
And each category goes up - it's especially of concern because roughly the damage increases by a factor of five. So if you go from a one to a four, you're looking at 100 to 150 times the amount of damage that could occur.
NORRIS: So why is it so difficult, of all things to predict or to forecast, the wind speed?
Mr. LANDSEA: It's much more involved with both the ocean and the atmosphere, whereas track predictions, it's all just the atmosphere pushing the hurricane around. And it also has to do with whether or not you get wind shear that disrupts the storm, whether you get dry air that sneaks into the inner core and dries out the thunderstorms, and whether you go over a patch of cool water.
So it's very much more difficult because of all these different interactions going on.
NORRIS: Now, I know that forecasts are based in part on computer modeling, but how do you actually pull data from the field?
Mr. LANDSEA: Well, that's part of the tricky issue, is that hurricanes occur over the open ocean. There's no weather balloons, there's no automated ground stations out there, so you got to put resources or instruments in the way of the hurricane to help measure what's going on. One of the best ways we do that right now is with satellite imagery. We're also very fortunate in the Atlantic and Gulf area that we have the aircraft reconnaissance that fly into the storms. What we're finding, though, for wind-speed forecasts is, we need detailed information on the inner core - say, the innermost 50 or 100 miles from the eye of the storm. And the best way to get that, that we can come up with right now, is with manned reconnaissance: Go in, get the data - especially radar data that has the winds and the rain - and get that into the computer model so that can help us make a better forecast.
NORRIS: Pardon my ignorance in asking this question, but would it be possible to use unmanned aircraft?
Mr. LANDSEA: Well, NOAA's investigating that option, as well. In fact, this week, that group of scientists are going to Barbados to use a small, unmanned aircraft called the Aerosond - that has a 10-foot wingspan - and see if they can fly it into either insipient storms or even full-blown hurricanes. So that's an option being explored.
NORRIS: Now, we're speaking to you in Miami. And there's another storm headed your way. It's named Hanna. What's the forecast for that one?
Mr. LANDSEA: Well, Hanna currently, right now, is not a very organized system, fortunately. The prediction for it is for it to slowly start moving northwest and then parallel the Florida coast, and perhaps make a landfall in the Carolinas on Friday night or Saturday. The intensity forecast - the wind-speed forecast - is much more difficult, and it's anticipated it could become a minimal hurricane. But given our errors we have now, it could be a tropical storm, could be a Category 1, could even be a Category 3. So that's why we, you know, we need to do a better job on this, because of these very big uncertainties just two or three days out in the future.
NORRIS: Well, Christopher Landsea, thanks so much for speaking with us.
Mr. LANDSEA: Yeah. Glad to help out today.
NORRIS: Christopher Landsea is the science and operations officer at the National Hurricane Center in Miami.