Transcript 100509Tucson_TropConf_Didlake.ppt

Comparison of secondary eyewall and
principal rainband in Hurricane Rita (2005)
Willoughby 1988
Anthony C. Didlake, Jr. and Robert A. Houze, Jr.
29th Conference on Hurricanes and Tropical Meteorology
May 14, 2010
Hurricane Rita (2005)
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Observed during RAINEX project using
NCAR ELDORA radar
Captured both principal rainband and
secondary eyewall in exceptional detail
Unique opportunity to compare the
internal dynamics of the two on the
convective scale
Better understanding of the structural
changes that must occur during the
process of secondary eyewall formation
Principal rainband
w
Downdrafts
Hence and Houze (2008), Didlake and Houze (2009)
Along-band average of vertical velocity
Didlake and Houze (2009)
Reflectivity (dBZ) as black contours
Reflectivity at 4 km
dBZ
Courtesy of Michael Bell
Vertical velocity at 4 km
w (m/s)
Azimuthal average of vertical velocity
Secondary eyewall
Reflectivity (dBZ) as black contours
Azimuthal average of vertical velocity
Principal rainband
Reflectivity (dBZ) as black contours
Azimuthal average of vertical velocity
Secondary eyewall
Reflectivity (dBZ) as black contours
Horizontal wind
Tangential velocity at 4 km
Vt (m/s)
Azimuthal average of tangential velocity (m/s)
Vertical vorticity at 4 km
(wavenumbers 0 and 1 removed)
ζ’
(10-3 m/s)
Tangential velocity perturbations
Vt’ (m/s)
w’ (m/s)
Vorticity perturbations
downwind
ζ’
(10-3 m/s)
w’ (m/s)
Vertical velocity perturbations in red/blue contours
Tendency equations of mean tangential
momentum and mean vorticity
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Cylindrical coordinates
Averaged over total storm
Vertical profiles of mean terms and
perturbation terms in secondary eyewall
perturbation
mean
vorticity
Mean
Radial profiles Terms
of mean and
perturbation
terms below
4.8 km in
secondary
eyewall
Perturbation
momentum
momentum
Terms
vorticity
Conclusions
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Secondary eyewall convection differs from
principal rainband.
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No preferred radius for convective drafts in
secondary eyewall.
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Below ~5 km,
• vortex-scale motions increase vorticity in inner
portion of the developing eyewall,
• convective-scale motions decrease vorticity in
outer portion.
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Mean and perturbation motions act together
to build the Vt max in the new eyewall.
Personal Acknowledgments
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Michael Bell
Stacy Brodzik
Brad Smull
Current dataset
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ELDORA radar on board NRL aircraft
1800-1820 UTC
Wind field retrieved using global
minimization technique (Gamache
1997, Reasor et al. 2009)
2-step Leise filter, ~5 km minimum
resolvable wavelength
Additional fields removing
wavenumber-0 and wavenumber-1
This research was supported by
NSF Grant ATM-0743180 and NASA Grants NNX07AD59G and NNX10AH70G and the NDSEG
program