Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
254 PM EDT Fri Oct 04 2019

Valid Oct 04/1200 UTC thru Oct 08/0000 UTC

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

12Z Model Evaluation with Preferences and Forecast Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend...Northwest and Northeast U.S.
            12Z GFS/UKMET/ECMWF blend...Plains/Midwest
Confidence: Slightly above average

The large scale flow pattern across the CONUS over the next few
days will feature multiple progressive northern stream troughs.
This will consist of a trough early in the period across the
Northeast which will advance quickly east across portions of
southeast Canada and the offshore waters tonight through Saturday.
Meanwhile, a strong upper trough already advancing inland across
the Great Basin and the northern Rockies will move east across the
Plains and Midwest through Saturday while taking on a negative
tilt. This will drive cyclogenesis in the lee of the Rockies which
will advance northeast across the upper Midwest and western Great
Lakes region. By later and Sunday and Monday, the guidance
indicates a new trough then beginning to amplify down toward the
Northwest U.S. as the trough over the Plains/Midwest weakens a bit
and moves downstream across the remainder of the Great Lakes
region and the OH Valley.

The models are in very good agreement with the mass field
evolution of the height falls exiting the Northeast and with the
new trough digging toward the Northwest by early next week, but
there are differences with the details of the troughing crossing
the Plains and Midwest. The 12Z GFS appears to be a bit too
energetic with its closed mid-level low circulation over the
Dakotas which is driving a stronger surface low compared to the
remaining guidance. However, overall, the 12Z NAM and to some
extent the 12Z CMC are possibly a tad too weak. The latest
ensemble means favor a solution generally a little stronger than
the NAM/CMC camp and closer to the 12Z UKMET/ECMWF solutions at
least through 60 hours. Thereafter as the energy dampens out and
moves further east, the GFS comes into better agreement with the
multi-model consensus.

A general model blend will be preferred across the Northeast and
the Northwest, but a blend of the GFS, UKMET, and ECMWF will be
preferred with the trough across the Plains and Midwest.


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

Orrison