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Nov.
9, 2007: Meteorologists' jaws dropped as Hurricane
Humberto slammed the Texas shore early morning September 13,
2007. At first just a nameless tropical depression, the storm
marshaled 85 mph winds and heavy rains in the blink of an
eye, demanding its identity as a category one hurricane.
 "It
made the transition from tropical depression to hurricane
within 24 hours right before landfall. It was a record breaker,"
says NASA atmospheric scientist Robbie Hood.
Right:
Humberto, photographed by the MODIS instrument aboard NASA's
Terra satellite. [Larger
image] [More]
Why
did Humberto leap to hurricane force so quickly? More importantly,
how could its rapid summoning of dangerous power have been
predicted so people on shore could have been forewarned?
These
questions are much on the minds of hurricane forecasters.
Humberto is only the latest example; two years ago, the busy
hurricane season of 2005 was notable for its rapidly intensifying
storms. No one knows if this is the start of a trend, but
everyone would like to see improvements in forecasting storm
intensity.
"Forecasting
intensity is one of the biggest problems we have right now
with hurricanes," says Hood. But Hood and her team of
researchers at NASA's Marshall Space Flight Center are making
strides toward solving that problem with a new invention called
HIRAD, short for Hurricane Imaging Radiometer.
Computer
models used to forecast hurricanes need to know wind speeds
at the base of the storm. Winds close to the eye, in the eyewall,
are especially important—but those winds can be the most difficult
to measure.
Enter
HIRAD: Designed to operate from an airplane or satellite,
"HIRAD will see from above through a hurricane's heaviest
rains and thickest clouds to measure the intense winds at
the surface of the ocean," says Hood.
HIRAD
measures the wind over water by sensing its froth. "Strong
winds sweep and swirl across ocean waves, whipping up foamy
white froth," explains Hood. "HIRAD measures microwave
radiation naturally emitted by this froth; the stronger the
winds, the more froth, and the more microwave radiation."
HIRAD
will measure a wider swath of area than traditional aircraft
tools, so fewer aircraft passes will be necessary. It is smaller
and lighter and requires less power than current wind measuring
instruments. It has no moving parts. It's relatively inexpensive
to build and has potential for satellite applications. All
positives.
Above:
Satellite-derived wind speeds at the base of Hurricane Humberto.
"Note how winds are not shown for the thickness parts
of the clouds. We hope to be able to fill in that gap with
HIRAD," says Robbie Hood.
A
later version of HIRAD will be proposed to measure wind direction
as well as speed. "For the best picture of what's happening
inside a hurricane, you need to know both wind speed and direction.
We'll look at the thickness of the foam on one side of the
wave as opposed to the other. This will give us the wind direction,"
explains Hood.
HIRAD
could take its first trial run on an aircraft as early as
the 2009 hurricane season and is expected to pass with "flying"
colors. Then, if funding is made available, it will fly on
a satellite. "When
you fly an instrument on a satellite, it helps everybody on
the globe," she says. "It improves forecasting around
the world, for countries that don't have the ground-based
radar and aircraft instruments larger countries have."
Karen
Stephens, HIRAD Project Manager, adds, "In the post-Katrina
era, it is especially satisfying to be working on something
so immediately beneficial and possibly life-saving."
But
first HIRAD has to prove itself and win funding to continue
its development. Until then, during hurricane season, don't
blink your eyes!
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Author: Dauna Coulter | Editor:
Dr. Tony Phillips | Credit: Science@NASA
| More
to the story... |
| Credits:
MSFC is partnering with the National Oceanic and Atmospheric
Administration, the University of Michigan, the University
of Alabama in Huntsville, and the University of Central
Florida to develop HIRAD.
How
does HIRAD compare to current technology? Robbie
Hood of the MSFC answers, "Current technology can
produce images of ocean surface winds from satellites
during light rain conditions. Current tools can also
give us ocean wind observations without imagery from
low flying aircraft. But HIRAD will be the first instrument
to produce imagery of ocean wind conditions from above
the hurricane during the heaviest rain and strong wind
conditions. Observing the winds from above the hurricane
provides better coverage of the conditions."
Previous
Science@NASA hurricane stories:
Dusty
Hurricanes -- (Science@NASA) Do dust storms trigger
hurricanes? NASA researchers fly into a dusty hurricane
to find out.
Birthplace
of Hurricanes -- (Science@NASA) Researchers are
gathering in the Atlantic ocean to catch hurricanes
in the act of being born.
Electric
Hurricanes -- (Science@NASA) Three of the most powerful
hurricanes of 2005 were filled with mysterious lightning.
The
Nameless Hurricane -- (Science@NASA) In 2004, a
no-name hurricane crashed into Brazil, surprising forecasters.
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