Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
142 PM EST Sat Nov 10 2018

Valid Nov 10/1200 UTC thru Nov 14/0000 UTC

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

12Z Model Evaluation...with Final Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: 12Z GFS/12Z ECMWF/12Z UKMET blend
Confidence: Average

...19Z update...

The previously faster CMC slowed down with its 12Z cycle
concerning the base of the upper trough axis across the southern
Plains on Tuesday, but remains a bit faster with the leading edge
of height falls across the lower Mississippi valley and with the
western Gulf of Mexico surface low. The 12Z ECMWF also trended
slower with the base of the upper trough axis into the southern
Plains which increases model mass field differences but the 12Z
ECMWF surface low is still within the acceptable ensemble low plot
spread. The 12Z UKMET did not change much from its previous cycle,
and therefore given these trends from the ECMWF/UKMET/CMC, there
are no recommended changes to the model preference.

...previous discussion follows...

Broad, longwave troughing in place over the lower 48 early this
morning will sharpen with the mean mid-upper level trough axis
shifting eastward to the Mississippi Valley through Tuesday.
Embedded within this flow is a departing mid-level closed low over
southern Quebec and multiple shortwaves over the western U.S. and
western Canada. One of these shortwaves will cross the Four
Corners region on Sunday as additional shortwave energy drops
south from Montana and Wyoming. Interaction between these two
features and a northern stream trough over the upper Mississippi
Valley will translate into a highly amplified flow with a surface
cyclone organizing over the Gulf Coast on Monday...tracking to the
Northeast for Tuesday. Upper riding along the West Coast will be
disrupted as the base of upper troughing, located in the Gulf of
Alaska, moves into southern British Columbia.

Model differences begin appearing around F036 hours (00Z/12) with
the 00Z CMC a bit faster with the shortwave trough axis crossing
the Four Corners region which continues into early next week. The
12Z NAM ending up a bit slower with the southern portion of the
longwave trough axis over the southern Plains and is also on the
northern end of the deterministic /ensemble guidance with a
surface low in the western Gulf of Mexico Monday morning.

Outside of the 09Z SREF mean, the ensembles (GEFS/ECMWF/CMC) show
decent agreement with only a small minority of ECMWF ensembles
supporting the slower 12Z NAM. There remains some timing/amplitude
differences though in the ensembles with the 00Z CMC members
fastest followed by the 00Z GEFS members and with the 00Z ECMWF
members slowest. The preference is to stay nearest to the best
clustering of members which is supportive of the past 4 cycles of
trends. This is closest to a blend of the 00Z ECMWF, 12Z GFS and
00Z UKMET.


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

Otto