Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1246 PM EDT Tue Oct 02 2018

Valid Oct 02/1200 UTC thru Oct 06/0000 UTC

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

12Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of 00Z ECMWF/EC Ens Mean; 12Z GFS; 06Z GEFS
Confidence: Average

The pattern across the CONUS will continue to gradually trend
toward a highly amplified western trough and eastern ridge, but
the specifics of how exactly this occurs are still in some dispute
among the models. Three key elements will have a large bearing on
the eventual evolution: (1) trough digging into the Pacific
Northwest at the moment, (2) closed low off the coast of
California, (3) trough currently near the Aleutians. As these
troughs progress into the Western US and interact, a large, broad
trough is expected to develop.

The 12Z GFS, 12Z NAM, and 00Z UKMET appear to progress shortwaves
through the northern stream faster than the other models, and the
GFS even faster than its ensemble mean. The 00Z ECMWF and EC
Ensemble Mean are slower. The preference is for a compromise of
this timing, with a slight lean toward the ECMWF, given the
support from the GEFS mean. Therefore, a blend of the GFS, GEFS,
ECMWF, and ECMWF Ensemble seems reasonable. The 00Z CMC showed a
much different trough structure than the other deterministic
models and is not favored at this time.

With other elements of the overall pattern across the CONUS, a
blend of the aforementioned models also seems appropriate and
should create a reasonable consensus forecast. Their timing of the
southern extent of the digging wave by Friday is very similar,
while the NAM and CMC show different timing with that feature as
well. Finally, a blend of these models should lead to a better
consensus in terms of the amplitude of the ridge along the East
Coast, with the NCEP models less amplified, and the other
deterministic models more amplified.


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

Lamers