Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1126 PM EST Sat Nov 17 2018

Valid Nov 18/0000 UTC thru Nov 21/1200 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: General model blend, with more weight toward the 00z
GFS, 12z UKMET
Confidence: Average

The synoptic pattern over the CONUS currently features an
anomalous upper level ridge off the west coast followed by a
positively titled trough over the central Rockies with an embedded
shortwave over the central US. Fast zonal flow exists across the
eastern US. Through the forecast period, the ridge off the west
coast will begin moving inland while the central/eastern trough
deepens. Another piece of mid-upper level energy off the southern
California coast will open up as it moves into the Southwest US.
Finally, at the end of the forecast period, a more significant
mid-upper level trough will approach the west coast.

The 00z models show relatively good agreement in the large scale
upper level pattern through the forecast period. Some differences
are noted with the closed low opening up across the Southwest US
late in the forecast period. The 00z NAM is strongest with the
feature through 84 hours, while the CMC dissipates the feature by
then. The 00z GFS and 12z ECMWF offer similar solutions and show
good agreement with the more significant trough approaching the
west coast at 84 hours.

At the surface, a quick moving area of low pressure is forecast to
track across the northern tier of the US into early next week,
deepening some off the New England coast Tuesday. The GFS/NAM
solutions show a low track closer to the coast compared to the
ECMWF, which takes the system further east by Tuesday afternoon.
The 12z UKMET looks more like the GFS solution, while the 12z CMC
trends closer to the ECMWF. This affects QPF for the period, with
the GFS and NAM solutions showing more QPF across New England
while the ECMWF has significantly less.

As a result, for most of the CONUS, a general model blend will
suffice, with the only exception being the surface low track off
New England, where more weight is given toward the GFS/NAM/UKMET
solutions given model trends.

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

Taylor