Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1204 AM EDT Mon Aug 26 2019

Valid Aug 26/0000 UTC thru Aug 29/1200 UTC

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

00Z Model Evaluation with Preferences and Forecast Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall Pattern Across the CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average through 60hrs slightly above average
after
Exception: 00z GFS/NAM w/UKMET/GEFS/ECENS at lower weight (Coastal
Low)
        
The 00z NAM/GFS continued another cycle of consistency and strong
deterministic guidance agreement with the synoptic
pattern/evolution over the CONUS.   As with any run, there are
some very small scale amplitude differences, as well as,
differences due to convective development/feedback.  The largest
differences in the mass fields/QPF axes, are driven by slight
timing differences with the frontal zone crossing the Northeast
and the interaction with the moisture feed from the the
tropical/subtropical surface wave to the Southeast Wed into Thurs.
The UKMET is a bit faster and it along with the 00z NAM suggest
slightly earlier deep moisture flux for some heavy rainfall across
SE ME.   This is interesting, given the spacing between the UKMET
and NAM is probably the largest spread with the surface wave, and
the UKMET is stronger than the NAM. Overall, the deep closed low
in S Canada and the frontal zone spread is small enough to support
a general model blend, but the surface wave off the coast has
moderate spread.  The ECMWF has once again become fast and strong,
paired closest to the UKMET, while the GFS and NAM are weakest and
draw westward due to the approaching height-falls.  The CMC also
bends left but is very strong by the end of Day 3, which does not
seem a good fit to continuity and the ensemble suite.  Overall
would favor a NAM/GFS solution with some lower weighted UKMET and
some ECENS/GEFS mean in the blend.

Elsewhere, there is a small timing issue with a strong shortwave
across NW Canada on Day 3.  The 00z NAM and 12z UKMET are too
fast, though with little sensible affect to even the northern tier
of the CONUS, but would shade away from those in a larger scale
blend.  So overall a general model blend is supported, with only
exceptions noted above, with an above average confidence through
about 60hrs before reducing to slightly above average afterward.


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

Gallina