Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1259 PM EDT Fri Aug 16 2019

Valid Aug 16/1200 UTC thru Aug 20/0000 UTC

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

12Z preliminary Model Evaluation...Including Preferences and
Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of the 12Z GFS, 00Z ECMWF, and ECENS/GEFS mean
Confidence: Slightly above average

Flow across the CONUS will remain broadly cyclonic through the
forecast period, although subtle height rises are likely Sunday
into early next week. This broad cyclonic flow persists in
response to repeated replacement of a longwave trough axis, first
across the eastern CONUS through Saturday, then shifting to the
West by Sunday into early next week. Shortwaves rotating through
the flow will be the primary sensible weather makers, and it is
discrepancy among these features that lead to the preferred blend.

The most notable differences involves the 12Z NAM which continues
to be a strong outlier with several of these vort lobes shedding
around a complex of upper lows in Canada. Through day 2 /Sunday/
the difference is rather minimal, but by day 3 the energy is much
too strong, as well as a southern outlier, when compared to the
global consensus and the ensemble envelope. The 00z UKMET
continues its trend of being too warm with its heights/thicknesses
across the CONUS, but most notably develops an impressive low at
the tail end of a cold front in the Gulf and lifts it into the
eastern Carolinas early next week. While the ECMWF and GFS both
show hints of energy in this same position, they are much weaker
and more realistic compared to reality based on current progs. The
CMC is generally too fast with many of these impulses, outpacing
the rest of the global guidance.

While QPF will likely be significant near FL and the Southeast, as
well as within any embedded shortwaves traversing the middle of
the CONUS, there still remains enough uncertainty in placement and
amounts to hedge away from the extreme numbers forecast by the
UKMET and NAM. For consistency and to remove some of the small
details, a blend of the ECMWF/GFS and their associated means
remains preferred.


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

Weiss