Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
317 PM EDT Fri Jul 05 2019

Valid Jul 05/1200 UTC thru Jul 09/0000 UTC

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

12Z Final Model Evaluation...with Confidence and Preferences
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...Overall Pattern Across the CONUS...
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Preference: GFS/ECMWF/NAM with limited CMC
Confidence: Slightly Above average

19Z Update: 12Z CMC has now instead of a shortened wavelength
trough in the NW on day 3, broad cyclonic flow as the shortwave is
absorbed into the parent closed low across Alberta/Saskatchewan.
This is significantly different than the remaining global suite,
and causes concern about including it despite its reasonable
evolution downstream and with the shortwave moving towards FL. The
UKMET continues to be an outlier with its mid-level heights across
the east. The 12Z ECMWF has weakened considerably with the
important FL shortwave, the first time it has reversed trend in
several runs, but is still included as it remains well clustered
with the global consensus.

Previous Discussion:
The general synoptic pattern through the forecast period will be
one of a slowly deepening trough in the west, with subtly lowering
heights within a broad ridge across the east. With the trough
amplifying in the west, a general model blend is appropriate as
the envelope is pretty small. However, the CMC features a notably
shortwave wavelength due to a stronger closed low south of Alaska
driving an inverted trough into the ridge. This creates minimal
overall sensible differences however, so it can still be included
in the blend.

Across the eastern 2/3 of the CONUS, a closed low southeast of
Hudson Bay will drop southward, gradually lowering heights within
the large scale ridge. The UKMET continues its recent trend of
being much too warm with its heights and thicknesses, in some
places more than 6dm above the global mean. At the same time, the
shortwave progged to drop towards FL by day 3 is much weaker with
the UKMET, likely due to its stronger ridging, and the UKMET
should be excluded. This feature moving towards FL is the most
notable in the east, and while the GFS/NAM are a bit weaker than
the ECM/CMC, the trend has been for a stronger feature so the NCEP
models are included in the preferred blend. Note that since this
feature is pretty small, the ensemble means are washing out some
of the intensity, so while the ECENS and GEFS do show this
feature, the deterministic models may be a better solution at this
time.


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

Weiss