Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1147 PM EST Sat Mar 09 2019
Valid Mar 10/0000 UTC thru Mar 13/1200 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
00Z NAM/GFS Evaluation Including Preliminary Preferences and
Confidence
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...Positively tilted shortwave trough moving east into Manitoba
and Ontario into Monday morning...
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Preference: 00Z NAM, 00Z GFS, 12Z ECMWF blend
Confidence: Slightly above average
Only minor timing/depth differences remain with this system, but
the 12Z UKMET and 12Z CMC are slower than the strong remaining
consensus led by the 00Z NAM, 00Z GFS and 12Z ECMWF which are in
agreement with the latest ensemble means,
...Surface low tracking across the Great Lakes today...
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Preference: General model compromise
Confidence: Slightly above average
Differences with this system are considered small enough such that
a general model blend can be used.
...Large closed low forming just offshore of California Sunday
night and tracking through Arizona and New Mexico Tuesday/Tuesday
night...
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Preference: 00Z GFS, 12Z ECMWF, 12Z UKMET blend
Confidence: Average
There is good agreement with this system until Tuesday morning
when the 00Z NAM begins to track the center of the closed low
south of the remaining model consensus. The 00Z NAM ends up with a
slower/farther south evolution of the eventual closed
low/negatively tilted trough axis into the Southern Plains. While
ensembles had been trending slower over their past few cycles, the
past 2 cycles have been consistent and with an upstream kicker, do
not think any slower trends will be seen. The 00Z GFS and 12Z
ECMWF are a bit faster than the 12Z UKMET but a blend of these
three models represents a favored middle ground. Meanwhile, the
12Z CMC is a bit faster than the latest consensus and this is
reflected in the latest ensemble guidance.
...Progressive upper trough approaching the Pacific Northwest
Tuesday morning...
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Preference: General model blend
Confidence: Average
The 12Z CMC is slower with a surface low approaching the coast of
British Columbia on Monday, but sensible weather impacts are north
of the border. Otherwise, the deterministic and ensemble guidance
shows good agreement, with the 12Z CMC toward the faster side of
the guidance with the leading edge of mid-level height falls into
the northern Rockies by Wednesday morning.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Otto