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| Dean: David Paulison, Administrator for FEMA, briefs reporters on preparations for Hurricane Dean on Sunday, August 19. The
National Hurricane Center began using new forecasting software this year. Charles Dharapak/AP |
Next forecasting challenge: predicting hurricane's wallop
Despite big improvements in predicting a storm's track, researchers struggle to peg its intensity.
By Peter N. Spotts | Staff writer of The Christian Science Monitorfrom the August 23, 2007 edition
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As the remnant of hurricane Dean spends itself over central Mexico, the 2007 Atlantic season's first major storm has earned a place in the record books. It's the third-strongest Atlantic hurricane ever recorded and one of a handful to strike land as a Category 5 storm – the most powerful rating for tropical cyclones.
It's also the kind of storm that can keep even day-shift forecasters at the National Hurricane Center awake at night. That's because, despite strong gains in predicting the track of these storms, forecasters still struggle to figure out how powerful they will become.
"When you look at the statistics for the last 25 years, you see very little improvement" in intensity forecasts compared with track forecasts, says Chris Davis, an atmospheric scientist who focuses on storm-forecast research at the National Center for Atmospheric Research (NCAR) in Boulder, Colo. "It is a very difficult thing to do." Researchers and forecasters are making progress, if glacially. This year, for example, the National Hurricane Center began using new hurricane-forecasting software that takes advantage of a broad range of information from satellites, hurricane-hunter aircraft, and other sensor platforms.
The new model "is designed to assimilate much more data," says Isaac Ginis, a hurricane researcher at the University of Rhode Island's Graduate School of Oceanography in Narragansett, R.I. The results are encouraging enough so that the new model will replace the old model soon, he adds.
Indeed, forecasters were fairly accurate in predicting hurricane Dean's ferocity. By the evening of Aug. 17, the National Hurricane Center said the storm would at least be on the verge of becoming a Category 5 within the next 72 hours. Dean crossed that threshold on Aug. 20.
But compared with track forecasts, which generally rely on large-scale wind patterns in the atmosphere, intensity forecasts rely on data from the ocean as well as the atmosphere. And the processes they must account for take place on time and spatial scales that challenge the current generation of computers and forecast software.
For example, researchers are keenly interested in what happens to sea spray and sea foam under and near a storm's eye walls, where tropical cyclones pack their fastest winds. These processes at the interface of ocean and atmosphere are the toughest to study because they occur where most instruments don't survive for long.
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