Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
336 AM EDT Thu Jun 20 2019

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

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

00Z Model Evaluation...with Final Confidence and Preferences
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...Overall Pattern Across the CONUS...
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Preference: General Model Blend
Confidence: Average

...07Z update...

The 00Z UKMET sped up across the West while the 00Z CMC slowed
down, closer to the remaining model consensus concerning the
mid-upper level shortwave on Saturday. Little change was noted in
the 00Z ECMWF compared to its previous 12Z cycle. The convergence
of models with the 00Z cycle shows less spread, outside of the
faster 00Z GFS. A general model blend is recommended which would
only nudge the western trough a bit faster with inclusion of the
GFS as part of an equal weighting of the 00Z deterministic
guidance.

...previous discussion follows...

There will be two main mid-upper level systems through Sunday
morning across the lower 48, one out West and the other exiting
the East Coast. Differences across the eastern U.S. are relatively
minor and do not escalate until the exiting trough and
corresponding surface low are near Nova Scotia. Therefore, a
general model blend should be acceptable for the East.

Out West and into the Great Plains, Timing differences show up by
Saturday morning with a shortwave in the southern portion of a
longwave trough extending from south-central Canada into the Great
Basin. The 12Z UKMET is slowest, while the 12Z CMC is fastest.
Ensemble spaghetti heights and trends over the past 4 cycles
support a middle ground which has been represented well by the
ECMWF mean. Currently, the closest middle ground is a combination
of the 00Z GFS, 00Z NAM and 12Z ECMWF.

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

Otto