Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
326 AM EDT Mon Jul 22 2019

Valid Jul 22/0000 UTC thru Jul 25/1200 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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...Much of the CONUS...
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Preference: General Model Blend
Confidence: Above Average

07Z Update: Some subtle differences exist with respect to
placement and intensity of shortwaves moving through the
amplifying longwave trough across the east. However, the non-NCEP
models remained in very good continuity with their previous runs,
so no changes are needed in the preferred blend.

Previous Discussion:
The overall model envelope is minimal even by day 3 with both the
temporal and spatial evolution of a cold front swinging across the
east, dropping an impressive longwave trough with it. The GFS may
be a bit on the fast edge and is quicker than its ensemble mean,
while the NAM lags the consensus a bit with its timing. However,
even these are acceptable differences at synoptic scales, and see
nothing of significant to rule out any of the global suite at this
time.


...Desert SW...
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Preference: Non-NAM Blend
Confidence: Slightly Above Average

07Z Update: Although some intensity differences exist with the
strength of the ridge by Wednesday, notably the UKMET and ECMWF
holding onto higher heights for a longer duration, the overall
spread of the ridge setup and position is minimal. The exception
continues to be with the NAM handling of shortwave energy rotating
into the ridge to enhance monsoonal moisture.

Previous Discussion:
With a ridge developing across the desert SW which will funnel
some monsoonal moisture northward through the period, the NAM is
very robust with a shortwave breaking down into the center of the
ridge and then rotating westward beneath it days 1-2. This is not
echoed by any other guidance, and produces QPF that is much
greater across NM/AZ than the remaining suite. The ridge is
strong, and it seems unlikely a shortwave of this intensity could
break it down so robustly as shown by the NAM. Do expect some
higher QPF in the southwest this period, and this is reflected in
the remaining guidance, but the NAM should be used with caution
across this area.

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

Weiss