Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
229 AM EDT Thu Aug 22 2019

Valid Aug 22/0000 UTC thru Aug 25/1200 UTC

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

00Z Model Evaluation Including Preferences and Forecast Confidence
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...Overall Pattern Across the CONUS...
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Preference: General Model blend
Exceptions: Non-NAM in Northeast
            ECMWF/UKMET blend in Gulf/FL by Day 3
Confidence: Slightly above average except Gulf/FL (below average)

07z update: A slight slowing in the UKMET/ECMWF and availability
of the 00z CMC suggest the 00z GFS is a bit fast exiting with the
shortwave into the Central Plains on Sat into Sun, in line with
typical bias but still serviceable if tempered slightly in the
blend and so a general model blend could be supported at slightly
above average here. 

The Great Lakes to Northeast cyclone continues to be strongly
agreed upon with exception of the 00z NAM, so will continue with
the same Non-NAM blend here at slightly above average confidence.

The SE Gulf/Florida wave continues to show moderate to high
spread, though the ECMWF has trended slightly stronger and
northeast of the GFS/NAM over the center of FL but still not as
deep as the UKMET, so will trend toward a UKMET/ECMWF blend but
still a below average confidence for this system.  As for TS Ivo,
a slight acceleration in the short-term in the 00z ECWMF over the
12z run, suggests a 50/50 blend of the ECMWF/GFS is closest to the
03z NHC forecast.

---Prior Discussion---
GOES-WV mosaic denotes two amplified troughs crossing the northern
portion of the CONUS and southern Canada.  The western system
continues to be quite impressively curved/compact crossing through
the lower Columbia River Valley; which is forecast to
break/stretch into a more positively tilted trof as the northern
stream accelerates eastward across Central Canada.  The global
guidance continues to present a very consistent and agreeable
development, even as the wave weakens crossing into the High
Plains Sat, giving way to upscale development of convection in
north-south moisture stream.  The UKMET is a bit slow here, and
the 00z GFS a bit fast, but overall a general model blend could be
supported with the evolution in this wave.

Further east, the deep, broader cyclone over James Bay is pressing
a weak shortwave through SE Ontario with a strong jet helping to
press the attendant surface front through the Great Lakes back
toward the the lower MO River Valley.   A secondary shortwave will
drop south out of Manitoba/W Ontario by early Friday, sharpening
the trof into a positively tilted trof across SE Canada into the
Southern Great Lakes. Eventually, by late Sat, the trailing edge
of the trof is expected to break into a small cut-off low across
New York into New England, this is a typically uncertain evolution
particularly in strength/depth and placement but the guidance is
fairly agreeable, though the 00z GFS shifted a bit faster (typical
of bias) relative to the UKMET/ECMWF.  Here, the 00z NAM is much
to strong in the northern portion of the wave and does not develop
as positively tilted, therefore with no wave break on the trailing
edge.  This evolution stands out against the ensemble and
deterministic suite to suggest a Non-NAM blend for this wave.

Elsewhere, there is moderate to high uncertainty to the
development of a surface reflection across S Florida by 12z Sunday
with the UKMET, over developed relative to other guidance (typical
of bias with these tropical systems).  The 03z NHC forecast for TS
Ivo, matches a blend of the ECMWF/GFS but closer to the 00z GFS. 


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

Gallina