Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
111 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 NAM/GFS Evaluation...with Preliminary Preferences and
Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of 12Z ECMWF, 12Z 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 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. The 12Z ECMWF is a bit more amplified
with the 00Z GFS flatter and the ensemble means are in the middle
of the two with a blend between the 00Z GFS and 12Z ECMWF
preferred. The GFS/ECMWF blend also holds true across the Gulf
Coast with surface low positioning, with the 00Z GFS/12Z ECMWF in
agreement with the ensemble means and the 12Z UKMET, while the 00Z
NAM and 12Z CMC lie 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, 12Z ECMWF/UKMET) or North Dakota
(00Z GFS/12Z 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 12Z ECMWF represents two camps
of ideas that are not all too different from the ensemble means.


...Hurricane Willa...
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Preference: General model blend closest to 03Z NHC advisory

The NHC forecast generally lies between the 12Z UKMET (on the
faster end of model guidance with the approach of the hurricane to
Mexico) and the remainder of the deterministic models -- 00Z NAM,
00Z GFS, 12Z ECMWF and 12Z CMC.

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