Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
108 PM EDT Sat Aug 04 2018

Valid Aug 04/1200 UTC thru Aug 08/0000 UTC

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

12Z Model Evaluation Including Preferences and Forecast Confidence
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...Overall Synoptic Pattern across the CONUS...
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Preference: 00Z ECMWF; 00Z UKMET; 12Z NAM
Confidence: Slightly above average

The model preference for the short term forecasts was a blend of
the ECMWF, UKMET and NAM, with a general lean toward the ECMWF.
These models are fairly consistent and also reasonably similar to
ECMWF and GEFS ensemble means. The 00Z CMC was flatter with the
building ridge in the western CONUS, and lagged the trough further
west (slower) across the Western Great Lakes by early next week.
This was, in some areas, near the outer periphery of ensemble
spread, and thus the forecast seemed too be unlikely enough that
it was excluded. The 12Z GFS, meanwhile, offers fairly good
similarity to the other models in many areas, but does seem to
suffer from convective feedback in parts of the Midwest.
Specifically, it takes an MCS on Sunday Night in the central
Plains, and maintains a coherent vort max aloft and surface low
paired with a focused QPF max to the northeast. Other than in this
area, though, the GFS could offer a reasonable solution to include
in a blend.

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

Lamers