Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1142 AM EST Sun Nov 25 2018

Valid Nov 25/1200 UTC thru Nov 29/0000 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: General model blend, weighted to 00Z ECMWF/EC ENS
Confidence: Slightly above average

Through the first couple days of the forecast (Monday and
Tuesday), model similarity is generally very good, with the
deterministic models mass fields well within the full range of
ensemble spread. The amplified pattern with a large trough in the
eastern CONUS should offer fairly good synoptic predictability.

There has been a notable southward shift with the northern
gradient of the precipitation axis across the Great Lakes over the
past several cycles of the NAM and GFS, with the NAM showing
greater dry air encroachment and the GFS shifting the surface low
track slightly further south.

The greatest differences are with the evolution of the low-level
cyclone in the Northeast on Tuesday. The 12Z GFS has trended well
west and further inland with the surface low and is now
substantially different than the clustering of other model
forecasts. Therefore, the preference is to lean away from the GFS
in this area, and closest to the 00Z ECMWF and ECMWF Ensemble (of
which the vast majority of members are tightly clustered near the
deterministic run).

Otherwise, the greatest differences emerge by mid-week across the
West, mainly related to the downstream response from an eastward
extension of the North Pacific Jet. Models show more variability
as the western ridge begins to break down, and with the
development of a trough along the West Coast. The preference there
is to lean close to the 00Z ECMWF and ECMWF Ensemble Mean, which
appear to be representative of a larger model cluster joined by
the 00Z UKMET and 00Z CMC.


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

Lamers