Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1133 PM EST Sun Jan 20 2019

Valid Jan 21/0000 UTC thru Jan 24/1200 UTC

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

00z Model Evaluation with Preliminary Preferences
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...East Coast...
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Preference: Any of the operational models

The deep cyclone over New England as of Sunday evening will
gradually pull away to the north and east. Guidance is in strong
agreement in handling this large scale, well-defined system.


...Pacific System Traversing the Nation Through Wednesday...
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Preference: Blend of the 00Z GFS / 12Z ECMWF

A full latitude, positively tilted trough will move steadily
across the country, beginning in the western U.S. on Monday. Over
recent runs there has been some systematic bias showing up, with
ECMWF and its ensemble being slower and NCEP models being faster.
At present time the slowness of the ECMWF is more pronounced on
Day 1 into early Day 2, holding cold air back behind a stronger
low level wave in the central Plains states.  The ECMWF then syncs
a little better with the GFS at later times, although the
fast/slow biases still show up at the surface through Day 3.
Overall, these two models probably form the best starting point
for this system. The 12Z UKMET certainly was on the deep side at
the base of the trough in the Southwest, and the UKMET has not
handled this system very well thus far. The 12Z Canadian looked
good through Day 2, but then hangs back on the slow side - slower
even than the ECMWF. The NAM produced an odd solution that looks
pretty good through Day 2, and then inexplicably accelerates the
low level frontal zone at break-neck speed on Day 3.


...Pacific Northwest Tue / Wed...
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Preference: Blend of the 00Z NAM/GFS and 12Z Canadian

A concentration of low amplitude troughing is expected to move
through a mean ridge position and onto the West Coast Wednesday.
Model spread has been noteworthy for several consecutive model
cycles, with some solutions like the 12Z UKMET being remarkably
fast, and others like the recent ECMWF runs holding onto a more
pronounced vort max at a more southerly latitude around 45 deg
north. The better looking consensus over the long haul of multiple
model cycles has been solutions more like the 00Z NAM/GFS in terms
of forward speed and in keeping most of the energy concentrated
farther north toward Washington and British Columbia. The 12Z
Canadian could also be thrown in the mix as being in good
agreement with the NCEP guidance.

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

Burke