Elvia Thompson<br />Headquarters, Washington January 12, 2004<br />(Phone: 202/358-1696)<br /><br /><br />Rob Gutro<br />Goddard Space Flight Center, Greenbelt, Md.<br />(Phone: 301/286-4044)<br /><br /><br />RELEASE: 04-017<br /><br /><br />A "HOT TOWER" ABOVE THE EYE CAN MAKE HURRICANES STRONGER<br /><br /><br /> They are called hurricanes in the Atlantic, typhoons in <br />the West Pacific, and tropical cyclones worldwide; but wherever <br />these storms roam, the forces that determine their severity now <br />are a little less mysterious. NASA scientists, using data from <br />the Tropical Rainfall Measuring Mission (TRMM) satellite, have <br />found "hot tower" clouds are associated with tropical cyclone <br />intensification.<br /><br /><br />Owen Kelley and John Stout of NASA's Goddard Space Flight <br />Center, Greenbelt, Md., and George Mason University will <br />present their findings at the American Meteorological Society <br />annual meeting in Seattle on Monday, January 12.<br /><br /><br />Kelley and Stout define a "hot tower" as a rain cloud that <br />reaches at least to the top of the troposphere, the lowest <br />layer of the atmosphere. It extends approximately nine miles <br />(14.5 km) high in the tropics. These towers are called "hot" <br />because they rise to such altitude due to the large amount of <br />latent heat.Water vapor releases this latent heat as it <br />condenses into liquid.<br /><br /><br />A particularly tall hot tower rose above Hurricane Bonnie in <br />August 1998, as the storm intensified a few days before <br />striking North Carolina. Bonnie caused more than $1 billion <br />damage and three deaths, according to the National Oceanic and <br />Atmospheric Administration National Hurricane Center.<br /><br /><br />Kelley said, "The motivation for this new research is that it <br />is not enough to predict the birth of a tropical cyclone. We <br />also want to improve our ability to predict the intensity of <br />the storm and the damage it would cause if it struck the <br />coast." The pioneering work of Joanne Simpson, Jeffrey <br />Halverson and others has already shown hot towers increase the <br />chance a new tropical cyclone will form. Future work may use <br />this association to improve forecasts of a cyclone's <br />destructive potential.<br /><br /><br />To achieve their goal, Kelley and Stout needed to compile a <br />special kind of global statistics on the occurrence of hot <br />towers inside tropical cyclones. The only possible data source <br />was TRMM satellite, a joint effort of NASA and the Japan <br />Aerospace Exploration Agency. "Many satellites can see the top <br />of a hot tower, but what's special about this satellite's <br />Precipitation Radar is that it gives you 'X-ray vision' so you <br />can see inside a hot tower," Kelley said. To compile global <br />statistics, the radar needs to be orbiting the Earth.<br /><br /><br />After compiling the statistics, Kelley and Stout found a <br />tropical cyclone with a hot tower in its eyewall was twice as <br />likely to intensify within the next six hours than a cyclone <br />that lacked a tower. The "eyewall" is the ring of clouds around <br />a cyclone's central eye. Kelley and Stout considered many <br />alternative definitions for hot towers before concluding the <br />nine-mile height threshold was statistically significant.<br /><br /><br />Funding for the research was provided by NASA's Earth Science <br />Enterprise. The Enterprise strives to advance Earth System <br />Science and to improve the prediction of climate, weather and <br />natural hazards from the unique vantage point of space.<br /><br /><br />For more information about the research and images on the <br />Internet, visit:<br /><br /><br />http://www.gsfc.nasa.gov/topstory/2004/0112towerclouds.html<br /><br /><br />For information about the TRMM Satellite on the Internet, <br />visit:<br /><br /><br />http://trmm.gsfc.nasa.gov<br /><br /><br />http://www.eorc.nasda.go.jp/TRMM<br /><br /><br />For information about NOAA's National Hurricane Center, visit:<br /><br /><br />http://www.nhc.noaa.gov<br /><br /><br />For information about Hurricane Bonnie, visit:<br /><br /><br />http://www.nhc.noaa.gov/1998bonnie.html