Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
129 AM EST Thu Nov 29 2018

Valid Nov 29/0000 UTC thru Dec 02/1200 UTC

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

00Z Model Evaluation...with Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall Pattern Across the CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of 00Z GFS, 00Z ECMWF, 12Z EC ENS, 00Z CMC
            Weighted most strongly toward ECMWF/EC ENS
Confidence: Average

---06Z UPDATE---
No change to the preliminary preference. The GFS, ECMWF and CMC
still represent the favored cluster and remain close to the 12Z
ECMWF Ensemble Mean with their evolution of the Plains cyclone.

---PREVIOUS DISCUSSION---
We are at the beginning of a significant pattern change, from
largely zonal flow at the moment, to a large and highly amplified
trough over the western and central CONUS this weekend. As with
most significant pattern changes, there are some model differences
that are important for QPF. To sort through these differences, the
preference was based most substantially on macro trends in the
past several model cycles.

Some of the more important trends have occurred with the strong
wave that will push through the West over the next couple days and
then eject in a negatively tilted fashion over the Plains, leading
to strong cyclogenesis and eventually an occluding cyclone. From a
pattern recognition standpoint, would anticipate a rapidly
occluding surface low in the Plains that will quickly become
tucked under the mid-level low.

This evolution is best represented by the 12Z ECMWF and ECMWF
Ensemble, and to a slightly lesser extent the 12Z CMC. Notably,
the 00Z GFS has continued a multi-cycle trend and is now much
closer to the ECMWF cluster.

The trend for the entire suite of models from 00Z last night to
12Z was significant, as they showed a substantially quicker
occlusion, and a trend toward a stronger surface low with a
sharper trajectory up into the Missouri Valley rather than out
into the Great Lakes.

The 12Z ECMWF Ensemble members were very tightly clustered, and
given strong overall model trends in that direction, and support
now from the CMC and GFS, the preference was to lean most closely
to the ECMWF and ECMWF Ensemble mean. This blend appears to be
reasonable enough in the West and the East to be applied more
broadly over the entire CONUS.


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

Lamers