Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
139 PM EST Sun Nov 04 2018

Valid Nov 04/1200 UTC thru Nov 08/0000 UTC

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

12Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: 12z ECMWF/GFS blend in eastern half of North America
            12z ECMWF/UKMET/NAM blend for Northwest/Rockies after
06/12z         
Confidence: Slightly Above Average in eastern half of North America
            Average in Northwest/Canadian Rockies after 06/12z.

19z update:
Little adjustments toward the 12z GFS by the UKMET/ECMWF, which
tightens the solution with between the ECMWF/GFS but the UKMET
remains a bit too far west/deep for most ideal blend.  The 12z CMC
has finally broken away from its outlier solution favoring the
wave along the border, now presenting a surface wave through the
Mid-MS valley into the Central Great Lakes, but still remains a
bit less than ideal given better consolidation of the GFS/ECWMF.  

Upstream, the negative...westward and due south push of the cold
air from the 00z ECMWF has moderated a bit to be more in line with
initial conceptual preference.  It remains strong but with a shift
eastward, seems more appropriate given larger scale setup and
regime over the North Central Plains.  The UKMET shifted this way
as well and both are starting to align best with an initially
middle ground solution of the 12z NAM.  As such with higher
confidence (average) will support a 12z ECMWF/UKMET/NAM preference
for the Northwest and North Central US (& Canada) after 06/12z.


---Prior Discussion---
Models try to consolidate on a common solution and appeared to
have done so with the lead wave lifting across the Midwest
currently as well as the general timing/spacing with the
approaching strong jet and shortwave along its nose currently in
the Intermountain West.  Generally, there is growing consensus to
the shape but given the system takes a broad (global trof) yet
still negative tilt with the internal smaller scale lead shortwave
through MO/AR on early Tuesday developing a strong surface low
that rolls quickly from S IL into the Great Lakes with significant
deepening.  Small differences in timing and magnitude of latent
heat/upscale feedback from the convective development lead to
slight longitudinal differences in the sfc low track...with
fast/strong solutions like the 00z UKMET being west and flatter
solutions like the 12z GFS furthest east.  The 00z ECMWF is most
central and consistent within the global suite just a bit west of
the GFS; the 00z CMC is a clear outlier and like the 12z NAM
favors a stronger shortwave along the US/Canadian border closer to
the deeper cold air source.  The NAM has been similar to the CMC
but the 12z run while still strong aloft, is starting to intersect
lower level moisture flux/convergence further east toward the
ECMWF axis.  All in all, WPC will favor the ECMWF solution,
followed by the GFS and some NAM at times (not across the Northern
Plains with the deeper center shortwave as it slides eastward by
Wed).  Confidence continues to grow with this growing consensus
but given small timing difference lead to mild to moderate spread,
confidence cannot be above average. 

In the wake of the main shortwave/jet streak, there is large model
spread with the trailing/entrance region of the jet as well as the
mean trajectory of the deep Arctic cold pool that slowly marches
south out of Northern Canada.  The 12z GFS, like many prior runs
is quite quick, leading to a flatter solution and a NW to WNW
trajectory of the cold air toward the Central Canadian
Providences, supported by the NAM and CMC.   The 00z ECMWF is very
cold and compact with the wave descending out of Western Canada
(east of the Rockies), dominating the Pacific stream of energy in
the mass fields, and strong confluence across WA/ID/MT by 00z
Thursday the 8th, the UKMET supports the ECMWF generally, but not
to the magnitude.    Given downstream influences and typical
biases, it is likely clear that neither solution will ultimately
evolve in reality but would favor something closer to the ECMWF,
so a preference of the UKMET and ECMWF is favored but injected
with the NAM a bit to hedge a bit more middle ground.  Obviously,
confidence is not very high (slightly below average for this
region after 06/12z). 


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

Gallina