Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1130 PM EST Wed Feb 13 2019

Valid Feb 14/0000 UTC thru Feb 17/1200 UTC

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

00Z Model Evaluation...with Preferences and Confidences
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...Central to Eastern CONUS...
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Preference: Blend of the GFS/ECMWF/CMC, weighted more toward 12z
ECMWF
Confidence: Average

Several features will move across the central/eastern US in the
forecast period. One low off the coast of Maine will continue to
move northeastward and active lake-effect snows will continue in
its wake off Lake Erie and Ontario. Another strong cyclone is
forecast to develop across the central Plains and deepen as it
moves over the Great Lakes region then toward this weekend, a pair
of weaker surface lows will move across the southern US.

Through 16.00z, model differences across the central/eastern US
are minor enough to just go with a general model blend. Beyond
that, there are timing/strength issues that develop especially
with the low tracking across the southeast US (and the mid-level
shortwave races across the central Plains and lower Great Lakes).
The GFS offers its typical fast bias with the low already across
central NC by 12z Saturday while the NAM is slower (northern GA)
at the same time. The CMC is further north (south-central VA) and
finally the ECMWF is about in the middle of the operational models
(southwest NC). The ECMWF falls within its ensemble mean (and GEFS
mean) so a blend leaning toward that solution is preferred.

...Western CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of the 00Z NAM/GFS, 12Z ECMWF
Confidence: Average

One closed mid/upper level low off the California coast will
quickly move east into the interior Rockies as it dampens out and
opens up. A much larger, stronger closed low currently off the
B.C. and Washington State coast will then drift southward along
the West Coast through Saturday. Several embedded shortwaves will
rotate through this large scale feature, eventually featuring a
broad, large scale trough over the western US.

In the large scale sense, the operational models all depict this
scenario with fairly good agreement. The differences lie in the
smaller scale features and shortwaves that will be moving through
the flow. The GFS is on the faster side with several of the
shortwaves, especially later in the forecast period (Saturday into
Sunday) compared to the ECMWF and NAM. Bigger differences are seen
at the surface with the low track and position by Friday night,
where the operational models have the position ranging from
southern Oregon (GFS) to northern Washington (CMC). The
NAM/ECMWF/UKMET are roughly in the middle.

Given some of the uncertainty in the smaller scale features, will
show just average forecast confidence, but with the big picture
being relatively similar, a general blend of the 00z GFS/NAM with
the 12z ECMWF is preferred for this cycle.


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

Taylor