Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
303 PM EDT Tue Aug 06 2019

Valid Aug 06/1200 UTC thru Aug 10/0000 UTC

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

12Z Model Evaluation with Final Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall Pattern Across the CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend, less weight on 12Z UKMET/CMC
Confidence: Slightly above average

...19Z Update...
No big improvements in terms of the UKMET/CMC differences as
compared to the model suite.  Therefore, kept the previous
preferences. There are some variability that remains with the
mid-level activity on Day 3. However, the 12Z ECMWF has trended a
bit farther south which corresponds with the 12Z GFS which
increases confidence a bit in terms of placement for QPF.  

...Previous Discussion...
A ridge in the west will eventually migrate west over the next
couple days making room for an approaching trough along the west
coast.  Meanwhile, mid-level vorticity will help to
erode/deamplify the upper ridge across the Northern Rockies. Along
the east coast, troughing continues as mid-level energy rounds
another closed low moving into Ontario. 

Overall model guidance is in fairly decent agreement in terms of
mass fields with limited spread.  However, there are some oddities
with the UKMET/CMC as noted by the mid/upper level flow pattern,
especially associated with the trough approaching the west coast
and troughing in the east.  Also, mid-level energy rounding the
ridging axis across the Rockies into the Plains will help to lower
the heights and thus deamplify the pattern.  This makes sense with
the 12Z NAM/GFS and 00Z ECMWF on board.  However, the 12Z UKMET
and the 00Z CMC does not illustrate these features.  When looking
at the QPF, this could lead to some issues. 

While a general model blend is preferred, there are differences
with mid-level energy placement which hinges on the ridge and
trough axis in the east.  The 12Z GFS is farther south on Day 3
which would have implications in terms of QPF.  However,
continuity has shown these type of features to migrate farther
south in time. Therefore, kept it in the model blend for now given
it is not out of tolerance with the model/ensemble spread.  And as
previously mentioned, the wetter GFS solution in the West
continues to make sense given the considerable northward push of
moisture and available jet dynamics for large scale ascent.


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

Pagano