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NSF PR 01-62 - August 1, 2001
Media contact:
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Cheryl Dybas, NSF
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(703) 292-8070
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cdybas@nsf.gov
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Anatta, UCAR
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(303) 497-8604
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anatta@ucar.edu
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Program contact:
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Cliff Jacobs, NSF
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(703) 292-8521
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cjacobs@nsf.gov
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This material is available primarily
for archival purposes. Telephone numbers
or other contact information may be out
of date; please see current contact information
at media
contacts.
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Virtual Hurricanes: Computer Model Pushes the Frontier
"Diana" images available at: ftp://ftp.ucar.edu/communications
In a key step toward improving hurricane prediction,
scientists at the National Center for Atmospheric
Research (NCAR) in Boulder, Colo., have reproduced
in a computer model the fine- scale structure that
drives the birth and strengthening of tropical cyclones.
NCAR's primary sponsor is the National Science Foundation
(NSF), which also funded the research. NCAR scientists
Jordan Powers and Christopher Davis are presenting
imagery from their hurricane simulation this week
in Fort Lauderdale, Florida, at the Ninth Conference
on Mesoscale Processes, sponsored by the American
Meteorological Society.
The simulation, which used the NCAR/Penn State (University)
Mesoscale Model, Version 5 (MM5), marks the first
time a cloud-resolving simulation has been able to
reproduce the formation of a tropical cyclone, given
only information about atmospheric conditions on a
scale much larger than that of the cyclone. The breakthrough
points toward future forecasting power that will soon
be available. NCAR is part of a team now building
a model similar to the MM5, but with more advanced
capabilities, that will generate daily weather forecasts
for the National Weather Service (NWS) beginning in
2004.
"Improved skill in forecasting in a research setting
often does not quickly find its way into operational
forecast models," says Cliff Jacobs, program director
in NSF's division of atmospheric sciences. "This research
has the best of all possible results: improved forecasting
techniques that developed as a result of an investment
in research, that likely will quickly make their way
into operational models."
For their MM5 experiment, Davis and Powers studied
Hurricane Diana, which struck North Carolina in 1984.
Diana was chosen because of ample surface data and
because a well-defined nontropical low preceded its
formation. The MM5 successfully reproduced several
stages in Diana's development, from its original state
as a nontropical low to its intensification to hurricane
status more than a day later.
According to Davis, "One of the remaining mysteries
about hurricanes is how they form, especially when
they're influenced by midlatitude weather systems
that move into the subtropics and tropics. We hope
that by analyzing the mechanisms behind storm formation
in these simulations, we can make hypotheses of tropical
cyclone formation that can be tested using aircraft,
radar, and satellite data. We also hope to understand
what's needed to predict storm formation in operational
weather forecast models."
Computer models used for day-to-day weather prediction
have become increasingly adept at projecting a hurricane's
motion. Yet even the best models have little skill
in predicting intensity, especially the rapid strengthening
often noted in the most powerful hurricanes. Part
of the problem is that the compact core of a hurricane,
including the spiral bands of showers and thunderstorms
that gather and focus energy, can't be modeled in
sufficient detail on the computers and models used
for everyday forecasting.
The new Weather Research and Forecasting Model and
more powerful computers will allow for the type of
fine-scale detail in the MM5 to be simulated for daily
forecasting. The National Oceanic and Atmospheric
Administration, the University of Oklahoma, and the
U.S. Air Force are collaborating with NCAR on the
project.
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