Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
150 AM EST Thu Dec 13 2018

Valid Dec 13/0000 UTC thru Dec 16/1200 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 the 00Z GFS and 00Z UKMET
Confidence: Average

The latest model consensus continues to support an impressive
amplification of the large scale pattern over the CONUS during the
next 36-48 hours, with ridges setting up over the West and East,
as a deep trough digs across the central and southern Plains and
then becomes cut off from the main belt of the westerlies through
Friday. By the weekend, this deep layer closed low will break down
the ridge across the East and advance east toward the central
Appalachians and Mid-Atlantic region. Meanwhile, a northern stream
trough will be progressively crossing the Great Lakes and
Northeast. In general, the models are showing rather good
agreement with the depth of the closed low, and while there had
been more substantial differences relating to the placement of the
height falls as the energy advances east, the 00Z global models
have at least converged on a more agreed upon track. The ECMWF and
CMC which had been farther south with previous model cycles have
trended farther north and a bit faster with the closed low
evolution which puts these solutions and much better agreement
with the GFS and UKMET. Although, the ECMWF does still lag the
model consensus a bit and is on the south side of the model
spread. Meanwhile, the NAM is overall the farthest north solution.

There will be a secondary shortwave trough progressively advancing
in across the Pacific Northwest by Friday and then quickly
advancing downstream across the northern Plains and upper Midwest
by Sunday. The NAM/GFS solutions and especially the UKMET all tend
to have a bit more progression and at least some interaction with
the downstream closed low lifting from the lower MS Valley to the
Mid-Atlantic region. The CMC and ECMWF are the slowest solutions
with this trough. Given the timing and placement concerns of the
ECMWF and to a lesser extent the CMC with the southern stream
closed low evolution, and northern stream trough progression, the
ECMWF/CMC solutions will be downplayed at least for their mass
fields. Better model clustering, trends and the latest ensemble
guidance supports a solution closer to the GFS which has strong
agreement generally from the UKMET. Thus a GFS/UKMET blend will be
the larger scale CONUS mass field preference.


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

Orrison