Advanced Research WRF High Resolution Simulations of Hurricanes Katrina, Rita and Wilma (2005)
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Advanced Research WRF High Resolution Simulations of Hurricanes
Katrina, Rita and Wilma (2005)
Kristen L. Corbosiero, Wei Wang, Yongsheng Chen, Jimy Dudhia and Christopher Davis
National Center for Atmospheric Research
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The Advanced Hurricane WRF• Run in real-time at NCAR since 2004 when a tropical cyclone (TC) threatened to make landfall within 3-5 days
• Two or three domains (12, 4, 1.33 km) with two-way moveable nests that follow the hurricane center
• Initialized from GFDL at 00 UTC and/or 12 UTC
• Kain-Fritsch cumulus (12 km only), WSM3 microphysics, YSU PBL scheme, drag (Donelan) and surface enthalpy coefficients (Carlson-Boland) for TCs
• Available on the web at http://www.wrf-model.org/plots/realtime_main.php
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Davis et al. (2007)
2005 performance Seven tropical
cyclone forecast systems
AHW4WRF 4 km
OFCLNational Hurricane
Center official
GFDLGeophysical Fluid
Dynamics Laboratory
FSSEFlorida State
Super Ensemble
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Hurricane Rita
03 UTC 24 September
39 hr forecast
Column maximum reflectivity
4 km
Precipitable water
cm
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Hurricane Wilma
4 km Precipitable water
22 UTC 20 October22 hr forecast
05 UTC 24 October77 hr forecast
cm
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4 km03 UTC 8/29
HurricaneKatrina
Precipitable water
12 km21 UTC 8/28
1.33 km00 UTC 8/29
cm
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Kossin & Schubert (2004)
Corbosiero et al.
(2006)
Reasor et al. (2000)
Lewis & Hawkins (1982)
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Katrina Radar Reflectivity 20 UTC 28 August
Top: WRF 4 km(left), 1.33 km(right)
Right: ELDORA radar
RAINEX JOSS Field Catalog
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HRD/AOML/NOAA
1752
1930
2232
2036
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Katrina Wind speed
Left:
Dual Doppler 1725-1946 UTC
28 August
Right: WRF 1.33 km
18 UTC
Top: 700 hPaBottom: 900
hPa
HRD/AOML/NOAA
m/s
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Rita Wind speed
Left:
Dual Doppler 2015-2208 UTC23 September
Right: WRF 4 km
01 UTC24 September
Top: 700 hPaBottom: 900
hPa
HRD/AOML/NOAA
m/s
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Both the real and WRF vorticity profiles exhibit sharp gradients of vorticity and changes in the sign
of ∂ζ/ ∂r.
Such profiles satisfy the necessary condition for barotropic instability.
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Schubert et al. (1999)
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900 hPa relative vorticity
Katrina 1.33 km WRF
900 hPa wind speed
m/s
x 10-4 s-1
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The 1.33 km WRF simulation is most unstable to wavenumber 2, with significant wavenumber 1-4
instability.
The 4 km WRF simulation is most unstable to wavenumbers 1 and 2, with very little instability at
higher wavenumbers. Code provided by M. Montgomery and M. Bell
Linear stability analysis
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Questions and Unresolved Issues• Are model numerics and parameterizations playing a role in the abundance of triangular eyewalls?
• Do tropical cyclones pose a unique problem to WRF with their circular geometry and strong diabatic heating- vorticity generation feedback?
• Will 1.33 km WRF TCs always be too weak due to an abundance of eyewall asymmetries?
• What is the resolution dependence of these eyewall structures?
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Vertical motion (warm up, cool down)
185 m resolution Idealized WRF hurricane
simulation
The eyewall is predominantly circular
or elliptical, with transient higher
wavenumber structures.
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Future Work• Add another nest to the 1.33 km Katrina run to test resolution dependence
• Decompose the WRF output into its various wavenumber components and compare with observations
• Analyze the results of the 2007 hurricane season WRF 1.33 km runs We’re not
alone!
WRF 2km WilmaGFS
initialization
Brian EthertonUNC Charlotte