Hurricanes in the Atlantic Ocean typically start as thunderstorms that blow off the western coast of Africa. With the right environmental conditions, these tropical depressions gather strength from warm ocean waters and spin up to hurricane force with the help of spiraling winds. But it is only roughly one out of 10 such storms that complete this evolution and scientists do not have a clear understanding of what makes for a future tropical cyclone. Now NASA and the National Oceanic and Atmospheric Administration (NOAA) as well as British and French scientists have teamed to study the origin and development of these storms using satellite imagery (such as that depicting the first tropical depression of this season at right), aircraft observations as well as data from ground-based radar and weather gauges.
Robbie Hood of NASA's Marshall Space Flight Center and her colleagues will spend mid-August to mid-September capturing data on nascent hurricanes from the Cape Verde Islands, approximately 350 miles off the coast of Senegal in Africa. "Over time, as people have tracked where hurricanes start, several of them start in the Cape Verde area," Hood explains. "The perfect scenario is if we get the weather we want, the satellite is flying over it and we can fly under it." The scientists hope to discover what differentiates a future hurricane from a storm that dies at sea. To do so, however, they will have to fly NASA's DC-8 aircraft through the storms themselves. "We look down through the storm to see what the humidity, pressure, temperature and wind structures are and we fly through the storms at different altitudes to sample the dust and raindrops to see how it is made up," Hood says. "It gives us a chance to look at the storms in higher detail, like looking at it under a microscope."
Scientists already know that during the summer hot, dusty winds blow off the African coast but it is unclear whether these dust storms damp down hurricane activity or incite it by helping seed the clouds for rain. "They come pretty far off the continent, sometimes extending all the way to the Gulf of Mexico," Hood says. "What we would really like to be able to sample is a couple of these types of systems. Hopefully some of them are really dusty and some are not so we can see the difference."
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Paired with NOAA observers in Barbados, the scientists will be able to track storms over their complete life cycle in the Atlantic and thus refine the knowledge of the forces that shape hurricanes, thereby improving models and, ultimately, forecasting. But the researchers also hope that none of the storms prove damaging either at home in the U.S. or in their African spawning grounds. "These kinds of systems affect the African economy, too," Hood notes. "These storms have impacts on both societies." All the more reason to discover what gives them their awesome power.
