Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
255 AM EDT Wed Oct 09 2019

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

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

09/00Z Model Evaluation with Preferences and Forecast Confidence
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...Energy amplifying over Central Appalachians/Mid-Atlantic...
...Deepening surface low pressure off the East Coast...
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Preference: General model blend until 12.00z (non-NAM thereafter)
Confidence: Slightly above average

07z: The 00z ECMWF/CMC both show a greater cyclonic loop with the
occluded low and the UKMET backed off slightly to join the
ECMWF/CMC.  This places the GFS a bit outside of the stronger
deterministic cluster, but given ECENS and 00z GEFS solutions,
think the initial preference of a general model blend

The 00z guidance has not varied much in the short-term with the
evolution of the deep occluded low southeast of Long Island.  This
is a slight southeast shift over the 24hr period, but there is
much stronger agreement in the placement/depth of the smaller
scale features to build greater confidence.  As the cyclone
matures and breaks down, the 00z NAM breaks from consensus lifting
north toward Nantucket Island.  The 00z GFS, along with the 12z
UKMET are stronger with a secondary cyclone development at the
triple point, but overall a non-NAM blend is supported at slightly
above average confidence mainly after 12.00z (with general model
blend supported before).  


...Deep upper trough/closed low amplifying over the West...
...High Plains cyclogenesis...
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Preference: Non-GFS blend (mainly after 11.12z)
Confidence: Slightly above to above average

07z Update: A very small adjustment north of the 00z ECMWF/CMC,
places the 00z UKMET a bit further outside of the stronger
consensus.  Still, given this is a continuation of the trend,
think the initial non-GFS preference is solid after 11.12z.

---Prior Discussion---
Models show very good timing in the large scale with the evolution
of the deep closed cyclone in the Central Plains. The 00z GFS,
much like the 18z GFS, continues to hint at a slightly increased
split between the Polar and Subtropical jet, midday Fri which
leads to an off-balance downstream development later Friday into
Sat.  As such the, GFS is a bit slower and therefore south with
the surface cyclogenesis and greater negative tilt to the
upper-level closed low.  The 12z UKMET shows greater negative tilt
that the ECMWF/CMC and 00z NAM, but the overall timing/placement
of the frontal zone and QPF are more in the vein of the latter,
making the GFS the solid outlier.  As such will prefer a Non-GFS
blend at slightly above to above average confidence.


...Approaching Pacific shortwave trough with attendant surface
wave and front by Sat...
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Preference: Non-NAM blend
Confidence: Average

07z update: The CMC slowed a tad to match the weaker but faster
GFS but the ECMWF has trended a bit weaker and faster too, making
the NAM stick out a bit too much.  Significant weakening of the
UKMET all suggests a slight adjustment to support a non-NAM blend
works as it approaches the Northwest coast at the end of Day 3. 
Confidence remains average in this Non-NAM blend.

---Prior Discussion---
An elongated trof advances across the Gulf of AK Fri with good
agreement.  However, a break down phase in the trough occurs
thereafter; where increased shearing between the northern and
middle Pacific streams, leads to some amplification of the base of
the trof.  The 00z GFS, typical of a potential newer bias, is
generally weaker and less apt toward some amplification, but has
good timing within the ensemble suite.  The 00z NAM and 12z ECMWF
and CMC, all suggest a more sensible smaller compact wave to form;
however, the CMC is uncharacteristically advancing toward
Vancouver Island, early Sat and so is not favored at this time.  
The 12 UKMET is very aggressive with the cyclogenesis and is not
preferred.  As such a 00z NAM/12z ECMWF blend is preferred with
some inclusion (at lower weighting) of 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