Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
208 AM EST Mon Nov 19 2018

Valid Nov 19/0000 UTC thru Nov 22/1200 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: Blend of 00z GFS/NAM/ECMWF
Confidence: Slightly above average

07z update: The 00z ECMWF/CMC/UKMET came in relatively similar
with the rest of the 00z guidance with the surface low track
Tues-Tuesday Night off the New England coast. By the end of the
forecast period, an area of low pressure will approach the Pacific
Northwest. Here, the ECMWF/CMC are a bit faster compared to the
GFS/NAM/UKMET solutions. Overall, for the CONUS, a general blend
of the GFS/NAM/ECMWF is preferred.

---previous discussion---
Through the forecast period, quasi-zonal split flow will become
more amplified with a western ridge advancing east with downstream
troughing over the eastern US. A closed low off the southern
California coast will open up as it moves toward the Southwest US.
A series of weak surface lows will track across the northern tier
of the US.

Fairly good agreement in the model guidance for the large scale
pattern through the forecast period. For the eastern US, the
biggest differences continue to be centered on the surface low
track Tuesday-Tuesday night. The 12z ECMWF was a bit of an outlier
with a more eastward track compared to the 00z GFS/NAM and 12z
UKMET which are relatively clustered with a solution closer to the
coast. Given the trends in the models the past few days and better
model agreement, preference was given to the GFS/NAM solution.

Other model differences to note are with the shortwave coming out
of the Southwest US into Texas Wednesday. The CMC/UKMET are
outliers, showing the open wave too suppressed near the Mexico
border. The GFS/NAM and to some degree the ECMWF are better
aligned in location and magnitude. With the more significant
shortwave trough coming onshore Wednesday night into Thursday for
the California coast, the NAM is a bit faster compared to the
GFS/ECMWF.

With this in mind, the preference will be for a blend of the 00z
GFS/NAM with the 12z ECMWF, noting its eastward track with the
surface low off New England on Tues-Tuesday night.

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

Taylor