Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
257 AM EDT Sat Jul 20 2019

Valid Jul 20/0000 UTC thru Jul 23/1200 UTC

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

00Z Final Model Evaluation Including Preference and Confidence
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...Overall Pattern Across the CONUS...
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Preference: 00Z GFS/UKMET/ECMWF
Confidence: Average

07Z Update: The trend in the non-NCEP 00Z suite has been for a
more amplified trough developing in the east driving the cold
front into the Southeast. The overall spread amongst the 00Z runs
has decreased, and the CMC is at least usable through the period,
but for continuity and due to lack of run to run consistency of
the CMC, prefer to leave the blend as inherited. The UKMET/ECMWF
continue to show good agreement, have ensemble support, and show
minimal differences in even the smaller scale features.

Previous Discussion:
Synoptic flow will evolve over the next 3 days from large scale
ridging across the eastern 2/3 of the country to an amplified
trough-ridge-trough pattern across the CONUS, with the ridge axis
setting up from the 4 corners into central Canada. The guidance is
in reasonable agreement with this development, but feature subtle
differences in timing of the longwave trough development in the
east, as well as smaller scale mesoscale features moving through
the mean flow.

For the blend, the key differences involve the speed of the
trough/cold front in the east, and intensity/spatial differences
of a shortwave moving through the Plains Sunday. The NAM remains a
fast/strong outlier with its development of the eastern trough and
its placement of the cold front, and is likely overdone as
guidance tends to break ridges down too quickly, and it has no
support from the remaining suite. The CMC overall pattern is
reasonable, but its trough and ridge axes are shifted westward
several degrees from the remaining guidance which has significant
impact on QPF placement. While the GFS is more amplified with the
trough in the east than the preferred and consistent ECMWF/UKMET,
it has some ensemble support and good placement of heaviest QPF
across the CONUS, so including it, at least in a small percentage,
is supported.


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

Weiss