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Report
Realtime Analysis of Model ICs
Wallace Hogsett, NHC
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Introduction
• Part I: NHC diagnostics module
– This diagnostics system inputs data from GFS/GFDL/HWRF and outputs
figures of vortex structure.
– Goal is to facilitate inter-model comparisons of initial vortex structure
and gain insight into systematic characteristics of the various model
initializations.
• Part II: A look toward 2011
– EMC/NHC collaboration.
– More sophisticated and quantitative diagnostics.
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Example 1 – Tomas Approaches Jamaica
R34kt
R34kt
RMW
GFS
RMW
HWRF
Above: near-surface winds (shaded, kts), streamlines, and surface pressure (green dashed,
hPa) from the GFS (left) and HWRF inner nest (center), and GFDL inner nest (right) ICs.
GFDL
Approximate observed
locations of RMW and 34kt
radius (via P3 radar & SFMR).
* GFDL is superior to HWRF in this case in terms of constraining initial
storm size, which is key factor in the initial balance/imbalance issue.
* Suggestion: Leverage GFDL size constraint methodology.
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Example 2: Tomas’ Unexpected Weakening
• On Halloween, Tomas
weakened rapidly.
• HWRF predicted well the
rapid weakening.
• GFDL predicted intensification
prior to weakening.
• Was this HWRF success a
lucky coincidence?
Above: Time-series of minimum pressure (top) and maximum 10m winds (bottom) from HWRF
(red) and GFDL (green) forecasts. Figure courtesy of Vijay and the HWRF team at EMC.
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Example 2: Vertical Structure of Weakening Tomas
Dry layer
eastward
tilt
GFS
HWRF
GFDL
Above: South-north (top) and west-east (bottom) vertical cross sections of wind speed (shaded, kts),
horizontal wind barbs (kts), and vertical vorticity (contoured, x 10-4 s-1) taken through the center of the GFS
(left), HWRF nest (middle), and GFDL nest (bottom) initial conditions.
• Vertical cross sections suggest that the HWRF handled well a northeasterly vortex
tilt and the associated very dry layer directly above the vortex center.
• Why does HWRF capture this structure, but GFDL does not? Was a satellite dataset
assimilated into HWRF?
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Part I Summary
• NHC diagnostics module allows model-model
comparisons in near realtime (Stream1).
• It has brought to light some strengths and
weaknesses of the model initializations.
• As the Tomas example shows, initial vortex
structure may be critical for short-term intensity
forecast improvements.
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Part II: Looking forward to 2011
•
•
Continue to produce realtime diagnostic products.
– Possible expansion beyond initialization.
– Include other HFIP models (stream 1.5)?
Begin newly-formalized NHC-EMC collaboration, including
assessment of upcoming 2011 size correction upgrades, and begin
work on next-level diagnostics.
… example of nextlevel diagnostic
product:
Sfc convergence
field, hodographs,
Shear.
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Part II: Looking forward to 2011
• Goal: develop capability to calculate budget terms on
native grids to diagnose source of systematic model biases.
– feedback results to EMC
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Summary
• A diagnostics module developed at NHC has
enabled realtime analysis of operational model ICs.
• Some 2010 results, including the HWRF vertical
vortex structure and storm size, will hopefully aid
EMC’s continuing development efforts.
• In 2011, we hope to take on some of the more
difficult issues quantitatively (e.g., moisture
budget).
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