Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1246 PM EDT Mon Aug 12 2019

Valid Aug 12/1200 UTC thru Aug 16/0000 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: Blend of the 06Z GEFS mean/00Z ECENS mean
Confidence: Below Average

The synoptic evolution through the forecast period is generally
well agreed upon by the global suite, but smaller scale features
create discrepancies in the sensible weather and synoptic
evolution leading to a lower than average confidence forecast.

The 00Z UKMET continues to occasionally be somewhat of a stronger
outlier with its ridging across the southern U.S. through the
period, but the guidance does all agree on gradually advancing a
portion of the ridging westward into the Southwest. Meanwhile, a
series of relatively low-amplitude shortwaves will advance across
the Midwest, Great Lakes and into the East through the period
which will carve out a broad longwave trough involving much of the
northern and eastern U.S. The 12Z NAM overall is a little stronger
than the model consensus with the shortwave energy, and the 00Z
UKMET is on the weaker side. The 12Z GFS, 00Z CMC and 00Z ECMWF
are clustered in between. All of the models allow a cold front to
advance through the Midwest and into the East over the next few
days, but there is some spread with respect to a broad surface low
that should pressure along the front over the Mid-Atlantic and
Southeast. The 00Z CMC/ECMWF solutions are farther north with the
placement of the front and surface wave activity over the
Mid-Atlantic at the end of the period. The 12Z NAM/GFS solutions
and the 00Z UKMET are farther south. The NAM and UKMET also tend
to have a relatively stronger wave over the OH Valley versus the
rest of the guidance.

There is also spread across the Northwest by the end of the period
as the guidance favors a shortwave trough dropping in toward the
Pacific Northwest. The 12Z GFS is a progressive outlier and the
00Z UKMET is notably weaker than all of the guidance. The 12Z NAM
is the slowest solution, with the 00Z CMC/ECMWF solutions in
between the slower and faster camps.

Based on the model spread in the details of the energy in the
Northwest and along the East Coast by the end of the period, a
blend of the ensemble means will be preferred which are in
reasonably good agreement and offer a nice compromise solution at
this point across the CONUS.


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

Orrison