Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
259 AM EDT Mon Jun 17 2019

Valid Jun 17/0000 UTC thru Jun 20/1200 UTC

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

00Z Final Model Evaluation...with Confidence and Preferences
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...Overall Analysis Across the CONUS...
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Preference: Days 1-2: Non-CMC, low weight on UKMET
            Day 3: NAM/ECMWF with low weight on the GFS
Confidence: Slightly Above Average through day 2, Average on day 3

07Z Update: Spread begins to increase Wednesday into Thursday with
the evolution of more significant forcing in the vicinity of a
closed low and pivoting shortwaves dropping into the Pac NW. This
signals the beginning of a regime change with troughing in the
west and ridging in the east, but guidance is split on how quickly
this will evolve. The GFS/UKMET are quick to dig a shortwave
around the closed low and lower heights across the NW, likely due
to stronger jet energy centered around 20.00Z driving energy more
quickly from the NPac. With the UKMET continuing to show its
warm/ridge bias in the Southwest and now matching slightly better
the GFS, prefer to keep the blend with some consistency and
utilize less GFS by day 3. The CMC remains an outlier with its
shortwaves moving across the CONUS, and is again not included in
the preference.

Previous Discussion:
Pattern remains mostly stagnant through the next several days with
broad cyclonic flow enveloping much of the CONUS. In this regime,
the significant discrepancies involve sub-synoptic scale impulses
moving through the flow from west to east, which have limited
forecast viability beyond the short term. In this setup however,
it is these small scale features which produce the most
significant sensible weather, and thus timing and intensity of
these features is important.

With the current suite, the CMC is the obvious outlier with its
rapid progression of shortwaves moving across the CONUS. This has
been the CMC trend for several runs now, and it outpaces the
remaining global suite and the ensemble envelope. The UKMET
continues to trend towards higher heights across the
Southwest/Central CONUS in response to more rapid expansion of a
mid-level high off the Pacific Coast the latter half of the
period. The UKMET can be utilized with some weight, especially
outside of the region featuring these height anomalies, but the
CMC should be removed or used with extreme caution since CONUS
wide convection and QPF is primarily driven by these small scale
impulses in this pattern

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

Weiss