Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1205 AM EDT Thu May 09 2019

Valid May 09/0000 UTC thru May 12/1200 UTC

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

00Z Model Evaluation with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: Non-CMC blend
Confidence: Slightly above average
            Average to slightly below average Sunday

A fairly atypical synoptic pattern will continue across the CONUS
to end this week with a broad but weakly defined trough across
across the Northern Plains, evolving to a positive tilt trof as
the western shortwave in the trof, retrogrades into the Great
Basin by late Thursday, directing a strong Pacific wave through
northern Old Mexico, while the remaining northern stream trof digs
across the Midwest by Sun.  Broad southwesterly flow and an open
Gulf of Mexico, will continue to support convective complexes
across the Northwest Gulf Coast to continue significant flooding
concerns in SE TX to the Lower MS Valley.

Even though the pattern is abnormal and mildly complex, there is
fairly strong deterministic model guidance, including some of the
timing/placement of the upscale convective complexes.  The major
departure is the 12z CMC which has some timing and depth issues;
the main one being the very slow closed low developing in the
Southwest starting around 11/00z and becoming a clear outlier by
12/00z.  Otherwise the mass fields are pretty good.  The 00z NAM
trended a bit better with the digging trough across the Midwest on
Sunday matching the 00z ECMWF a bit more than the 00z GFS and 12z
UKMET, which show a slightly faster/less deep solution relative to
the slower/deeper ECMWF.

The only other issue in the solutions, appears to be related to
timing as well, and perhaps some manifestation of the difference
in the Midwest on day 3.   As the undercutting Pacific trough
reaches W TX around early Sat morning under good agreement (minus
the CMC as noted before).  As it shears into confluent flow across
the Lower MS Valley, the GFS/UKMET get a bit faster and
intersecting with return moisture flow and lingering
frontal/outflow enhanced boundary across the lower MS valley/SE
TX, the shortwave shifts more eastward along with the overrunning
QPF swath.  This is opposed by the slower ECMWF and 00z NAM, both
suggesting stronger isentropic ascent and higher QPF axis into the
lower TN and OH river Valleys late Sat into Sunday morning.  Each
model seems to be representing its typical late forecast bias (GFS
too fast, NAM to wound up, ECMWF too slow, UKMET too strong, but
too fast) and a more centralized solution both in timing, angle of
QPF axis and shortwave should be employed as best as possible.

As such a non-CMC blend is supported at slightly above average
confidence, with only average to slightly below average confidence
with the QPF axis at the end of Day 3 forecast period in the Lower
MS valley into the TN/OH Valleys and Mid-Atlantic (with the fast
solutions). 

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

Gallina