Forecasters travel to hurricane 'nursery' off Africa

From the Miami Herald (miami.com) Sat, Jul. 29, 2006

"Decoding a storm's DNA Sure, you can just sit there and wait for a fully developed hurricane to come along -- or you can spend a month 3,700 miles away in a hurricane nursery, studying the birth and maturation of storms that often grow into mass killers."

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South Florida scientists are joining a project to study hurricanes from their birth near Africa through their development in the Atlantic.

BY MARTIN MERZER
mmerzer@MiamiHerald.com

Decoding a storm's DNA

Sure, you can just sit there and wait for a fully developed hurricane to come along -- or you can spend a month 3,700 miles away in a hurricane nursery, studying the birth and maturation of storms that often grow into mass killers.

Forty scientists and others are choosing the second option. They are traveling to a cluster of islands near Africa, hoping to decode the secrets of the ferocious storms known as Cape Verde hurricanes.

''We're not sure what triggers these things to come together,'' said Jason Dunion, director of NOAA's Hurricane Field Program, based in South Florida. ``Some real mysteries are out there, and some of that is because we just weren't in position to study it.''

Cape Verde storms are those that form in the eastern Atlantic near the Cape Verde Islands, about 350 miles off Senegal in West Africa.

These hurricanes often grow into fearsome monsters simply because they have so much time to develop as they trek northwestward -- toward us -- over warm Atlantic water. Among recent Cape Verde storms: Hugo in 1989, Andrew in 1992, Floyd in 1999, Frances and Ivan in 2004 and Emily last year.

In addition, the remnants of two Cape Verde systems combined last August to help form Katrina, though it developed into a hurricane just off South Florida and intensified dramatically into a Category 5 powerhouse after it reached the Gulf of Mexico.

Scientists still cannot fully identify the factors that fuel that magnitude of intensification, but they also seek a better understanding of much more fundamental issues related to the development of hurricanes.

Chief among these: Why do some clusters of thunderstorms that move off Africa -- called tropical waves -- coalesce into hurricanes while others do not? And how do these benign batches of wind and rain acquire the tell-tale rotation that transforms them into potentially catastrophic hurricanes?

Between 60 and 70 tropical waves brush past the Cape Verde Islands during each hurricane season, but only 10 percent grow into tropical storms or hurricanes.

''This is one of the great mysteries of weather science,'' said Jeff Halverson, a hurricane scientist serving as a consultant to the study.

Answers to those mysteries will not come easily or quickly, and most of the information collected by the team will not immediately make its way into forecasts, but any new clues should help scientists provide better predictions in the future.

Combining resources, scientists from the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration and other institutions plan to employ ground instruments in the Cape Verde Islands and fly aboard a specially equipped DC-8 through storm seedlings.

They will measure winds, water vapor, moisture, atmospheric pressure, temperatures and the dynamics of cloud formation and development.

Then, they will ''hand off'' the systems to Dunion and other members of NOAA's field program, based at the agency's Hurricane Research Division on Virginia Key on the Rickenbacker Causeway.

Those scientists, also aboard research planes, will take measurements as the systems approach Barbados, St. Croix or Bermuda.

In both cases, researchers will focus much of their attention on the complex interaction between tropical systems and Saharan dust storms, which begin in Africa but often stretch across the Atlantic and can reach South Florida.

Called the Saharan Air Layer, the dry air and strong winds that distinguish this phenomenon generally suppress hurricane formation, though scientists yearn to learn more about the specks of dust within that layer and how they influence the formation of rain.

In the end, researchers hope to develop information that eventually can be melded into computerized models and otherwise serve as practical tools for hurricane forecasters.

Said Dunion: ``The idea is to help people know what to expect downstream.''