Ocean Surface Wind David E. Steitz

Headquarters, Washington, DC

Phone: 202/358-1730

Rosemary Sullivant

Jet Propulsion Laboratory, Pasadena, CA

Phone: 818/354-5011

RELEASE: 00-139

Tropical storms churning into potentially dangerous
hurricanes often hide behind a cloak of clouds. But NASA has given
forecasters a new way to peek under the covers and identify storms
much faster.

Scientists traditionally rely on satellite pictures to study the
telltale swirl of clouds of a forming storm. However, the SeaWinds
instrument aboard the QuikSCAT satellite can look through the
cloud cover and measure winds at the ocean’s surface.

According to a new study by National Oceanic and Atmospheric
Administration (NOAA) and NASA researchers expected to be
published in a major scientific journal, SeaWinds can detect the
closed circle of winds that characterize a tropical depression up
to 46 hours sooner than conventional means.

“The SeaWinds data can help us in two ways,” says paper author
Kristina Katsaros, director of NOAA’s Atlantic Oceanographic and
Meteorological Laboratory, Miami, FL. “They can detect tropical
depressions early and help us improve our models. With more
accurate information on the surface wind speed and direction in
hurricanes at all stages, our models can do a better job of
predicting a hurricane’s evolution and course.”

QuikSCAT was launched in June 1999. It travels over ninety percent
of the ice-free oceans every day with a high-frequency microwave
scatterometer that provides detailed information on sea surfaces
that can be translated into wind speed and direction.

In their NASA-supported study, Katsaros and her colleagues looked
at SeaWinds data from the regions where 12 of the named storms in
the 1999 hurricane season formed. Eight of the storms eventually
developed into hurricanes. The researchers then examined the data
collected 12 to 48 hours in advance of the storms being declared
tropical depressions.

While the SeaWinds instrument wasn’t always upstream of all 12
storms, it was in position to provide wind data on eight. In those
cases, it was able to detect the closed wind circulation well
before it could be seen as cloud swirls on the GOES satellite
image. The lead times ranged from three hours for Hurricane Irene
to 46 hours for Hurricane Lenny.

Being able to detect tropical depressions early is especially
important in increasing warning times in regions like the Gulf of
Mexico, where storms can grow quickly into hurricanes and can make
landfall within a few days. Early detection also may help the
National Hurricane Center plan the best use of its resources to
keep watch on developing storms.

“The ability of SeaWinds to see tropical depressions at their
earliest stage gives us the opportunity to identify and study the
elements that create hurricanes,” says co-author W. Timothy Liu,
the project scientist of SeaWinds at NASA’s Jet Propulsion
Laboratory, Pasadena, CA. The Jet Propulsion Laboratory built and
operates the QuikSCAT spacecraft for the Office of Earth Sciences,
NASA Headquarters, Washington, DC.

During the current hurricane season, scientists from the National
Hurricane Center and the Hurricane Research Division are comparing
SeaWinds data with wind information from computer models,
reconnaissance aircraft, satellites, and devices that measure
temperature, moisture and relative humidity.

In a separate study, Liu combined SeaWinds data on winds with
information from another instrument, the Tropical Rain Measuring
Mission. TRMM can also can see through clouds and measure rainfall
in hurricanes. “Hurricanes are especially devastating when they
are accompanied by strong winds and heavy rain,” says Liu.
“QuickSCAT and TRMM provide the only opportunity for us to view
the interplay between wind and rain before landfall and help us to
understand and predict hurricanes.” The results of this study
appeared in the June 6 issue of EOS, Transactions of the American
Geophysical Union.

“This year the QuikSCAT data will be incorporated into a surface-
wind analysis system of NOAA’s Hurricane Research Division to
produce the surface windfields in tropical storms in near real
time,” says Kastaros. “This will help the National Hurricane
Center in making decisions about warning the public when a storm
threatens landfall.”

QuikSCAT data are available from NOAA’s National Environmental
Satellite and Information Service on the Internet at:

Near real-time wind maps can be viewed or downloaded at:

Information on NASA’s Oceanography program can be found at: