Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1234 PM EDT Thu Aug 16 2018

Valid Aug 16/1200 UTC thru Aug 20/0000 UTC

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

12Z Model Evaluation...with Preferences and Confidence
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...Upper trough crossing the Midwest and Northeast...
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Preference: Blend of the 12Z GFS and 00Z ECMWF
Confidence: Slightly above average

While there is generally good agreement with the height falls
ejecting out of the Midwest through Friday, the 12Z NAM, 00Z CMC
and 00Z UKMET all generally get out of phase with the 12Z GFS, 00Z
ECMWF as the energy arrives across the Northeast this weekend.
Will prefer a blend toward the GFS and ECMWF given good ensemble
support for this cluster.


...Upper trough crossing the Midwest and Northeast...
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Preference: 00Z UKMET or 06Z GEFS/00Z ECENS blend
Confidence: Slightly below average

The models take the next in a series of troughs and dig it down
across the central Plains this weekend. The 12Z NAM and to some
extent 00Z ECMWF are the deeper solutions with this system. The
ECMWF is also tending to focus its surface low pressure wave a bit
north of the model consensus. The 12Z GFS actually appears to
possibly be a little slow with its trough evolution and also with
the placement of its surface front over the Plains. The 00Z UKMET
is closest to the model consensus and tends to at least spatially
be a bit better aligned with a blend of the latest GEFS mean and
ECENS mean, so will favor the UKMET.


...Trough digging across the Northwest by Sunday...
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Preference: Non-NAM blend
Confidence: Above average

A new upper trough and associated closed low will dig into the
Northwest by Sunday. The 12Z NAM is a little more progressive than
the global models with this feature, although all of the guidance
generally has good agreement on depth. Will prefer a non-NAM blend
here with this system.


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

Orrison