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VO: In order improve hurricane forecasts, scientists model storms of the past.

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Braun: We model old storms because it gives a way to

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compare the simulations to observations and try to assess the

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physical processes within storms and also how well those

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processes are represented in the forecast models. Because that's key to

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improving forecasts in the future.
VO: With improvements in computing power,

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researchers have been running ensemble forecasts.

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Braun: Instead of a single forecast, we run a whole series of forecasts where you make slight

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variations to the initial information that goes into the models and then see how much

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spread you get within those forecasts.
Running ensembles gives us a visual description

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of the level of uncertainty associated with forecasting tropical storms.

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Braun: And the average over all those ensembles usually gives you a better forecast

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than if you ran just a single forecast model.
VO: One way to test forecast models is to

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reanalyze past storms.
Reale: It's very important to study the

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worst possible storms in history because those are the ones that really put the

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system to a challenge.
VO: NASA and NOAA cooperate in satellite

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systems and sharing data, as well as experiments and modeling research, all of

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which enable NOAA and other agencies to provide better forecasts of tropical cylones.

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Reale: When NOAA and National Hurricane Center issues a forecast, the better the

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forecast is historically, the more likely it is that people would trust the

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forecast, and decision makers will make the right decisions and

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they will tell what place has to be evacuated and what place can stay.

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VO: To get a clearer look at the processes inside the hurricane, NASA's Global

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Precipitation Measurement Microwave Imager, or GMI, gives us an

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X-ray beneath the clouds.
Braun: If you have a storm that maybe isn't well defined, doesn't have

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a visible eye, with the GMI and similar instruments

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you're able to see the rainfall structure underneath those clouds

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So you can see the ring of heavy precipitation in the eye wall, as well as

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several of the rain bands. And that really helps to tell us a lot about how the storm is evolving,

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and how that might relate to the intensity of the storm.

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VO: Representing those small-scale eye processes in global models has been an ongoing

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area of research.
Reale: By increasing resolution and increasing, of course, the quality of

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the physical processes that are represented inside the model,

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global models have been getting better and better. They make hurricanes

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smaller, more compact, closer to the real size,

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and the eye becomes smaller and smaller and they become more intense.

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