Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
143 PM EST Sat Dec 01 2018

Valid Dec 01/1200 UTC thru Dec 05/0000 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: General model blend
Confidence: Slightly above average

19z update: Through most of the forecast period, model consistency
remains high. Some differences are noted toward the end of the
period across the western US with respect to the upper level low
moving in. The GFS continues to be a bit faster compared to the
rest of the guidance. Also of note is a shortwave dropping across
the Northern Plains, where there are some subtle
strength/placement differences. The GFS is a bit flatter compared
to the more digging ECMWF. The WPC preference continues to be a
general model blend.

---previous discussion---
Through 84 hours, the latest deterministic guidance shows good
agreement with the synoptic features and mass fields across the
CONUS. In the wake of the storm system across the central and
eastern US through 24 hours, sprawling high pressure from Canada
will bring relatively benign weather to much of the CONUS in the
later forecast period. As a result, model similarity is very high
and the WPC preference is for a general model blend.

One area of noted differences is the lingering/stalled frontal
boundary across northern Florida and portions of the Southeast.
While the spread among the guidance is low, there continues to be
QPF magnitude differences, where the 12z NAM is the most bullish
with a stripe of heavy rainfall across the FL panhandle into
southeast GA. The UKMET is displaced a bit southeast of this axis,
while the ECMWF/GFS are in a good agreement.

Another area of concern is across the western US associated with
the next upper level shortwave trough and surface low. The NAM/GFS
are faster bringing the feature onshore compared to the
ECMWF/UKMET. A blend would yield a reasonable solution for now.


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

Taylor