January 12, 2004

Elvia Thompson
Headquarters, Washington
(Phone: 202/358-1696)

Rob Gutro
Goddard Space Flight Center, Greenbelt, Md. 
(Phone: 301/286-4044)

RELEASE: 04-017

A 'HOT TOWER' ABOVE THE EYE CAN MAKE HURRICANES STRONGER

They are called hurricanes in the Atlantic, typhoons in the West 
Pacific, and tropical cyclones worldwide; but wherever these storms 
roam, the forces that determine their severity now are a little less 
mysterious. NASA scientists, using data from the Tropical Rainfall 
Measuring Mission (TRMM) satellite, have found "hot tower" clouds are 
associated with tropical cyclone intensification. 

Owen Kelley and John Stout of NASA's Goddard Space Flight Center, 
Greenbelt, Md., and George Mason University will present their 
findings at the American Meteorological Society annual meeting in 
Seattle on Monday, January 12.

Kelley and Stout define a "hot tower" as a rain cloud that reaches at 
least to the top of the troposphere, the lowest layer of the 
atmosphere. It extends approximately nine miles (14.5 km) high in the 
tropics. These towers are called "hot" because they rise to such 
altitude due to the large amount of latent heat. Water vapor releases 
this latent heat as it condenses into liquid.

A particularly tall hot tower rose above Hurricane Bonnie in August 
1998, as the storm intensified a few days before striking North 
Carolina. Bonnie caused more than $1 billion damage and three deaths, 
according to the National Oceanic and Atmospheric Administration 
National Hurricane Center. 

Kelley said, "The motivation for this new research is that it is not 
enough to predict the birth of a tropical cyclone. We also want to 
improve our ability to predict the intensity of the storm and the 
damage it would cause if it struck the coast." The pioneering work of 
Joanne Simpson, Jeffrey Halverson and others has already shown hot 
towers increase the chance a new tropical cyclone will form. Future 
work may use this association to improve forecasts of a cyclone's 
destructive potential.

To achieve their goal, Kelley and Stout needed to compile a special 
kind of global statistics on the occurrence of hot towers inside 
tropical cyclones. The only possible data source was TRMM satellite, 
a joint effort of NASA and the Japan Aerospace Exploration Agency. 
"Many satellites can see the top of a hot tower, but what's special 
about this satellite's Precipitation Radar is that it gives you 
'X-ray vision' so you can see inside a hot tower," Kelley said. To 
compile global statistics, the radar needs to be orbiting the Earth.

After compiling the statistics, Kelley and Stout found a tropical 
cyclone with a hot tower in its eyewall was twice as likely to 
intensify within the next six hours than a cyclone that lacked a 
tower. The "eyewall" is the ring of clouds around a cyclone's central 
eye. Kelley and Stout considered many alternative definitions for hot 
towers before concluding the nine-mile height threshold was 
statistically significant.

Funding for the research was provided by NASA's Earth Science 
Enterprise. The Enterprise strives to advance Earth System Science 
and to improve the prediction of climate, weather and natural hazards 
from the unique vantage point of space.

For more information about the research and images on the Internet, 
visit: 

http://www.gsfc.nasa.gov/topstory/2004/0112towerclouds.html 

For information about the TRMM Satellite on the Internet, visit: 

http://trmm.gsfc.nasa.gov 

http://www.eorc.nasda.go.jp/TRMM 

For information about NOAA's National Hurricane Center, visit: 

http://www.nhc.noaa.gov 

For information about Hurricane Bonnie, visit: 

http://www.nhc.noaa.gov/1998bonnie.html 

	
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