Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1251 AM EDT Tue Aug 20 2019

Valid Aug 20/0000 UTC thru Aug 23/1200 UTC

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

00Z Model Evaluation...Including Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of the 18Z GEFS/12Z ECENS means
Confidence: Slightly above average

Mid to upper-level ridging will persist through the forecast
period across the southwest U.S. while the northern stream energy
will become increasingly amplified featuring two troughs, one over
the Pacific Northwest and another across the Great Lakes region.

In the first 48 hours, model agreement is above average with
little spread seen in the 500 mb heights across the CONUS. As a
result, a general model blend can be applied for the mass fields.
Beyond this time frame, some notable differences are observed,
especially with the troughs across the Northwest and Great Lakes
regions. Typical model biases were seen, with the GFS and NAM
being a bit faster with the trough progression over the Northwest
and faster and farther northeast with the trough over the Great
Lakes and southeast Canada. The 12Z ECMWF though was seen as being
somewhat of a deeper outlier over the Northwest compared to the
rest of the model guidance. Also, the 00Z NAM was noted to be a
bit deeper with shortwave energy advancing across the OH Valley
and Mid-Atlantic region on Tuesday.

For the time being, the preference will be to lean toward a
consensus of the ensemble means for the CONUS per the 18Z GEFS
mean and 12Z ECENS mean.

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

Orrison