Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1123 AM EST Sun Jan 13 2019

Valid Jan 13/1200 UTC thru Jan 17/0000 UTC

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

00Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend -East
            Non-CMC up to 15/12z - West
             00z ECENS/06z GEFS means thereafter
Confidence: Above average except Pacific
             Below average after 15/12z

The east coast system will be shifting away from the coast later
this evening with fairly good agreement after the surface low
establishes off the coast, as there remains some east to west
variance in the precise cyclopedias, but fairly minor as any
solution is along a consistent axis/placement.   As the system
slides away the lingering trough over the TN Valley will also
quickly shift eastward providing a broad area of
westerly/northwesterly flow in the eastern half of the US.   A
broad vortex develops north of Hudson Bay but in a very stable
formation with peripheral shortwaves, including one clipping the
northern Great Lakes by late Tues into Wed.  Here the ECMWF/UKMET
are a shade north and less amplified than the CMC or 12z NAM/GFS
but still for day 3 there is strong agreement to further support a
general model blend East of the Rockies at above average
confidence.

For all the agreement East, the Pacific region continues to show
volatility and high guidance variation, especially after the
initial system breaks down entering California on Tuesday.  While,
this elongated closed low and moisture plume into Central and
Southern CA is agreed upon, the upstream timing/depth and
orientation play a significant role thereafter.  The 00z ECMWF/CMC
are uncharacteristically fast and that is due to the eastern side
of a larger central Pacific vortex shedding less energy eastward
which becomes fast and highly elongated.  The CMC further breaks
from the ECMWF with a strong vortex north of 50N which is only
marginally supported by the NAM.  So will ignore the CMC.  The 00z
ECMWF while supported by a large chunk of the ECENS members, it is
on the faster, southern side of the suite...and the ECENS mean is
much closer to the slower/northward solutions presented best by
the GEFS mean. The NAM is slow and deeper with this wave clipping
northern CA, though the 12z GFS picked up some pace and shifted
faster into N CA further separating from bulk of ensemble members.
 At least the GEFS presses a bit further south and shows the most
similarity to the overall trends over the last 3-4 ensemble
cycles, giving it the most central potion/shape.  The 00z UKMET is
somewhere in between in placement of the base of this trof, but
typical of its negative bias, it is very compact and fast.  All
considered, will be shifting to the ECENS/GEFS mean solution for
this wave, though with well below average confidence.  

Quick on the heels of this weaker/stretched out wave, is the core
of the larger scale vortex, producing a very strong, very broad
surface cyclone, timing of this wave is fairly similar, though the
UKMET/CMC remain well displaced.  The 12z GFS shifting faster with
the initial wave into N CA, allows for a more northward shift of
this main deep cyclone, very close to the GEFS mean and 12z NAM
and a bit NW of the stronger ECMWF.  Thinking the GFS/NAM are
likely a bit too fast with this system and the ECMWF is likely too
slow. So best to maintain the strength of the a 12z GFS/NAM and
00z ECMWF solutions but shift the centers/timing toward a middle
ground or between ECENS mean and GEFS mean locations. 

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

Gallina