Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1212 PM EST Sat Feb 09 2019

Valid Feb 09/1200 UTC thru Feb 13/0000 UTC

...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...

12Z Model Evaluation...with Preferences and Confidence
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...Western U.S...
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Preference: General model blend...through 60 hours
            Blend of the 12Z GFS/00Z CMC/06Z GEFS mean and 00Z
ECENS mean...after 60 hours
Confidence: Above average

An active weather pattern will continue to evolve as a series of
northern stream troughs/closed lows drop south just off the
Pacific Northwest. Already there is one shortwave trough that is
moving inland across California which the guidance has ejecting
progressively downstream across the Intermountain West tonight
before it ejects out into the Plains on Sunday. There is little
model mass field spread with this system as it crosses the West.
Meanwhile, a strong deep layer closed low currently seen in IR/WV
satellite imagery just offshore of WA/OR is settling gradually
down to the south. This energy will pivot inland across the Great
Basin and Rockies Sunday and Monday as a new deep layer closed low
drops down from southern B.C and across WA state. All of this
energy will shift off to the east out into the High Plains by late
Monday. There is reasonably good model agreement with the details
of these height falls through Monday. By Monday night and Tuesday,
there will be yet another deep layer closed low and associated
trough axis dropping south near and offshore of the Pacific
Northwest. The 12Z NAM becomes a deep outlier with this energy,
with the 00Z UKMET appearing to be too progressive. Gradually the
00Z ECMWF by the end of the period also appears to become a bit
too slow. The 00Z CMC clusters well with the 12Z GFS and there is
generally good support from the 06Z GEFS mean and 00Z ECENS mean
with this camp as well. Will prefer a general model blend across
the West through 60 hours, and then lean toward a blend of the 12Z
GFS, 00Z CMC, 06Z GEFS mean and 00Z ECENS mean thereafter.


...Central/Eastern U.S...
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Preference: 12Z GFS/06Z GEFS mean/00Z ECENS mean compromise
Confidence: Below Average

The lead shortwave trough that ejects across the Plains and Upper
Midwest on Sunday will gradually dampen out as it approaches the
Great Lakes region. The 12Z NAM appears to be a relatively deeper
outlier with this energy compared to all of the global models, and
a non-NAM blend can be preferred with this feature.

The next system will be the ejecting large scale trough out of the
West by Monday which will drive cyclogenesis over the Plains in
the lee of the central Rockies. The 12Z GFS remains a bit north of
the non-NCEP models with this low evolution through late Monday
and including the 12Z NAM. However, the 06Z GEFS mean is
supportive of the deterministic GFS, and there is at least modest
support from the 00Z ECENS mean as well. By Tuesday, the models
diverge rather wildly with the evolution of surface low pressure
as the longwave trough takes on a negative tilt. The 12Z NAM
ultimately ends up being stronger and farther north with the
entire height fall and surface low evolution. The 00Z CMC ends up
being much farther south and is on the south side of the model
suite. The 00Z UKMET ends up being a weaker and also more of a
progressive outlier with the system. The 12Z GFS and 00Z ECMWF
diverge latitudinally with the GFS north of the ECMWF low track,
and overall deeper and a bit more progressive. The GFS though is
not as far north as the NAM. The 06Z GEFS mean and 00Z ECENS mean
are more supportive of the determinsitic GFS and suggest the
non-NCEP models as a whole are too far south. However, given the
overall deterministic model spread, confidence is low as to the
ultimate low track evolution on Tuesday. For now as a compromise,
will favor a blend of the 12Z GFS with the 06Z GEFS mean and 00Z
ECENS mean.


Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

Orrison