Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
255 PM EDT Fri Aug 17 2018

Valid Aug 17/1200 UTC thru Aug 21/0000 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 Synoptic Pattern across the CONUS...
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Preference: Non_NAM blend
Confidence: Slightly above average

The pattern over the next few days will feature three main upper
troughs across the CONUS with one advancing into the Northeast
U.S., one entering the central Plains and Midwest, and a new upper
trough entering the Northwest by Monday. The 12Z global models
have come into better agreement on the details of all of these
troughs, and especially with respect to the troughs over the
Plains/Midwest and the Northeast. The 12Z CMC/ECMWF solutions did
trend a bit weaker and away from their stronger 00Z runs and their
respective 00Z ensemble suites. This is allowing for a
deterministic clustering toward the weaker/flatter GFS/UKMET
solutions. It is feasible the guidance could attempt to shift back
toward a stronger and more amplified trough, but given the latest
trend and clustering away from this, the preference will be the
weaker consensus. Elsewhere, the main piece of guidance that is
problematic is the 12Z NAM which is again too progressive with its
height falls across the Northwest and out across the central
Plains/Midwest. Based on all of this, the preference will be
toward a non-NAM blend across the CONUS.


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

Orrison