Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
254 PM EDT Wed Jun 12 2019

Valid Jun 12/1200 UTC thru Jun 16/0000 UTC

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

12Z Model Evaluation...with Confidence and Preferences

...19Z Update...

Model preference remains with very little adjustments noted by the
latest 12Z models.  A couple of differences observed were from the
UKMET and GFS.  It appears the UKMET might be a bit too slow with
respect to mid-level energy rounding the negatively tilted trough
across northern New England.  This thus results in a more
unrealistic surface pattern and QPF totals. The 12Z CMC seems a
bit more reasonable with its mass fields.  And the GFS, compared
to the latest model spread, toward the end of the period seems to
illustrate too weak of mid-level energy undercutting the ridge set
across western Canada.  While these features do illustrate
variability among the model, the difference are subtle at this
point with a general consensus among the mass fields.  However, it
should be noted that the CMC is a bit too robust with its surface
feature Wednesday into Thursday which still causes some concern
when putting trust in this model run; not much model continuity as
of late. Therefore, kept the model preferences at this time. 


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...Great Lakes/Ohio Valley/East Coast...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-CMC blend
Confidence: Slightly Above Average

Mid-level trough axis across the central CONUS will continue to
dig and eventually become negatively tilted as it progresses
eastward through Friday.  Models are in fairly decent agreement
with this feature, the subsequent shortwave energy and resultant
surface low across the Great Lakes.  However, there are
differences in regards to the timing and overall extent of the
vorticity within the mid-level.  The 12Z GFS is a bit faster with
the trough axis compared to the 00Z UKMET and EC/12Z NAM. The 00Z
CMC illustrates a much more amplified trough thus sinking farther
south and thus its timing slowed. Aloft, it appears the 12Z GFS
has a slightly faster and less narrow jet streak resulting in
stronger diffluence off the coast of the Mid-Atlantic and
Northeast.  This can be more readily seen at the surface where the
coastal low depicted by the 12Z GFS is farther offshore as
compared to the 00Z EC and UKMET/12Z NAM.  As a result, heavier
precipitation will remain offshore.  The 00Z ECMWF and UKMET/12Z
NAM solutions depict an area of heavy rain associated with the
surface low and is also assisted by the convergence associated
with the aforementioned surface low crossing the Great Lakes. 
While this difference would seem to cause great spread among these
 models (latest ECMWF/UKMET/GFS) , the 12Z GFS has been quite
consistent with its solution the past several runs and thus feel
it can not be ignored.  Therefore, the model preference would be
to favor a non-00Z CMC blend with the mass fields associated with
CMC seeming somewhat questionable.  As the trough axis shifts off
the northeast coast Saturday morning, the latest EC/NAM/UKMET/GFS
are all well clustered, especially with the long wave energy in
Ontario. The CMC however, is not. 


...Western and Southern U.S...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General Model Blend
Confidence: Above average

Elsewhere across the CONUS, as the exiting trough to the east
makes way for ridging across the west, shortwave energy will try
to edge into the Pacific Northwest.  As it does so, most model
guidance illustrates the energy weakening with some
restrengthening across the upper-Mid west with better height fall
anomalies.  The 12Z GFS has come on board with the 12Z NAM with
respect to the strong mid-level impulse.  However, when looking
aloft at 250mb for the same time, the NAM has a flatter, slightly
less amplified upper level pattern as compared with the 12Z GFS. 
Meanwhile, the 00Z ECMWF/UKMET seem to be well clustered in terms
of mass fields at most levels; though this clustering breaks down
by the end of the period.  Therefore, there does not seem to be a
consistent or strong level of continuity among the models given
such weak synoptic features.  Thus, feel a general model blend is
appropriate with ensemble means supporting this preference.  

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

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