Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
130 PM EST Fri Feb 08 2019

Valid Feb 08/1200 UTC thru Feb 12/0000 UTC

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

12Z Model Evaluation...with Preferences and Confidence
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...Eastern U.S...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

Good model agreement in the near term with the closed low and
surface cold front track/speed across the Great Lakes and
Northeast. Most of the energy with that system will pull north of
the CONUS by Saturday morning. With subtropical ridging anchoring
across southern Florida, relatively benign weather is in store for
the eastern U.S. and with the above average model agreement for
the mass fields. Thus, a general model blend will be preferred.


...Central/Western U.S...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend...through 60 hours
            Blend of the 12Z GFS/12Z ECMWF...after 60 hours
Confidence: Average

An active weather pattern is expected to develop across the
western U.S. through the forecast period with several impulses
moving onshore. Initially, a closed mid/upper level low near
39N/129W will advance east toward central California by tonight
and will then open up and advance quickly inland across the
Intermountain West on Saturday in response to much stronger height
falls associated with a deep trough/closed low settling south
across the Pacific Northwest. The lead energy will shear
downstream across the Plains and Midwest through Sunday, and the
models show good agreement with the mass field evolution of this
system.

The aforementioned closed low arriving over the Pacific Northwest
will settle south to near the CA/OR border by Saturday night and
will then shift inland across the Great Basin by Monday while
opening up into an open trough. Additional height falls associated
with yet another closed low feature will be dropping south from
British Columbia and down over the Pacific Northwest by Sunday
night and through Monday. The guidance is in good agreement with
the details of the first Pacific Northwest closed low feature, but
then more substantial model differences show up over the Pacific
Northwest by Monday with the additional energy settling south. The
12Z NAM in particular is notably out of phase with the global
models regarding its closed low evolution over the Pacific
Northwest after 60 hours as it drives a much stronger closed low
down over WA/OR versus the global model consensus which is
somewhat weaker and also advancing farther east toward the
northern Great Basin and northern Rockies by the end of the
period. The 12Z GFS and 12Z ECMWF have much better clustering with
the mass field details and at least modest support from the 12Z
CMC and 12Z UKMET.

Much of the energy associated with the first Pacific Northwest
closed low will be ejecting downstream across the Plains by late
Monday which will allow surface low pressure to develop in the lee
of the Rockies. The better model clustering with the evolution of
this energy and the surface wave development lies with the 12Z GFS
and 12Z ECMWF. The 12Z NAM, 12Z CMC and 12Z UKMET are a bit slower
by comparison, but there is overall a bit better ensemble support
for the GFS/ECMWF camp.

A general model blend can be preferred out through about 60 hours,
but thereafter, the preference will be strongly toward the 12Z GFS
and 12Z ECMWF as a consensus.


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

Orrison