Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1215 AM EDT Sat Oct 05 2019

Valid Oct 05/0000 UTC thru Oct 08/1200 UTC

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

00Z Model Evaluation with Preferences and Forecast Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend
           w/lower weighting to 00z NAM in TN Valley on D3
Confidence: Above average

The large scale flow pattern across the CONUS over the next few
days will feature multiple progressive northern stream troughs and
a tropical wave supporting surface development northeast of the
Bahamas and paralleling the Southeast Coast through Tues.  The
shortwave lifting out of the WY Rockies currently will progress
through MN into Ontario by Sunday with a draped but progressive
front progressing through the Midwest and Ohio Valleys with the
tail end flattened across the OK S Plains into Central MS/W TN
valley by the end of the forecast period.  Guidance continues to
be quite agreeable even through the Day 3 period, though typical
biases start to manifest by Day 3.  The 00z GFS is faster and
generally weaker with the trailing shortwave energy/frontal zone
in the MS/TN valley relative to the other guidance, while the 00z
NAM continues to be a bit stronger allowing for a bit of wave
development in the TN valley by late Mon/early Tues.  Still, both
00z GFS/NAM are trending toward a common solution with the
UKMET/CMC/ECWMF solutions.  The UKMET is like the GFS, slightly
faster and weaker in trailing boundary, while the ECMWF/CMC are a
bit slower and more amplified with a weak wave in TN (though not
as much as the NAM).   All in all, this is great agreement and a
general model blend can be employed with above average confidence,
though perhaps fading the weighting of the NAM after 72hrs in TN
Valley.

The tropical wave progressing across the Southeast Atlantic will
approach the Bahamas and start to turn north.  This increased
convergence and upper level baroclinic outflow/support will help
to deepen a surface wave off the coast.  The slower/stronger
southern shortwave solutions of the NAM/ECMWF/CMC support a
stronger surface wave while the GFS is a bit weaker.  The UKMET is
slow overall with the tropical wave and lags further.  However,
overall, there is solid guidance to support a general model blend
perhaps closer to the GEFS/ECENS mean solutions given the moderate
spread/uncertainty related to more random convective development
deepening the wave more or less dependent on the model and the
run.  As such a general model blend is supported but at average to
slightly above average confidence for this feature.  



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

Gallina