Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
246 AM EDT Tue Oct 23 2018

Valid Oct 23/0000 UTC thru Oct 26/1200 UTC

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

00Z Model Evaluation...with Final Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of 12Z ECMWF, 00Z GFS
Confidence: Average

The synoptic scale pattern over the next 3 days will feature
troughing in the Northeast with a series of shortwaves to pass
through. Upper troughing currently extending from Texas to the
Canadian Rockies will be pushed eastward as progressive but weak
upper troughing over the Southwest and stronger upper troughing
offshore of the Pacific Northwest translate eastward. By Friday
morning, an upper ridge will be centered offshore of California
with mid-latitude westerlies aimed into the Pacific Northwest.

The 00Z ECMWF/UKMET/CMC did not change significantly from their
prior 12Z cycles. The greatest differences were in the middle of
the country on Thursday and Friday with mid-level troughing. The
ensembles have trended into good agreement with timing over their
past 4 cycles, but differ on amplitude. Only the 00Z NAM stands
out as a faster outlier with this trough axis by 12Z/26.  The 00Z
ECMWF/CMC are a bit more amplified with the 00Z GFS/UKMET flatter
and the ensemble means are in the middle of the two camps with a
blend between the 00Z GFS and 00Z ECMWF preferred. The GFS/ECMWF
blend also holds true across the Gulf Coast with surface low
positioning, with the 00Z GFS/00Z ECMWF in decent agreement with
the ensemble means and the 00Z UKMET/CMC, while the 00Z NAM lies
north of the latest ensemble scatter low plots.

Differences also were present from the Northwest to the
north-central U.S. as the base of a shortwave trough axis reaches
south-central Canada (00Z NAM, 00Z ECMWF/UKMET) or North Dakota
(00Z GFS/00Z CMC). Ensembles and deterministic trends haven't been
all that helpful but tend to favor a position between the two
camps, perhaps closer to the northern ECMWF camp. Fast zonally
oriented flow into the Pacific Northwest by Friday morning shows
differences with the placement of embedded shortwaves and related
shortwave troughing/ridging. Confidence is on the low side here,
but a blend between the 00Z GFS and 00Z ECMWF represents two camps
of ideas that are not all too different from the ensemble means.


...Hurricane Willa...
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Preference: non 00Z CMC blend closest to 03Z NHC advisory

The NHC forecast generally lies near the 00Z deterministic
consensus except for the 00Z CMC which is significantly slower and
west of the 03Z NHC advisory for Willa. Please refer to the
National Hurricane Center for the latest information on the
forecast for Hurricane Willa, as well as discussion of model
preferences and forecast reasoning.


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

Otto