Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
141 PM EST Mon Jan 14 2019

Valid Jan 14/1200 UTC thru Jan 18/0000 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 the 12Z NAM/GFS/ECMWF
Confidence: Slightly above average

The large scale pattern over the next few days will feature a deep
vortex evolving near Hudson Bay which will gradually be shifting
down to the south. Underneath this energy will be a series of
fast-moving shortwaves moving through the central and eastern U.S.
through Tuesday for which the models are in excellent agreement
with. Meanwhile, the models show a well-defined shortwave moving
in from the Pacific Ocean and crossing the Intermountain region
through Tuesday, which then ejects out into the central Plains by
Wednesday. This energy then quickly crosses the mid-Mississippi
and Ohio Valleys on Thursday along with a weak area of low
pressure. The latest guidance shows some modest differences with
timing and depth, with the 12Z GFS a tad stronger with the
shortwave, and the 12Z UKMET now a bit faster with the energy, but
they are otherwise in good agreement on the larger scale.

By Thursday, the models have a more substantial trough advancing
progressively into the western U.S. which will bring significant
precipitation to California in particular. The 12Z NAM/GFS/ECMWF
solutions show very good agreement with the timing and depth of
the trough. The 12Z CMC is also close to this multi-model
consensus, but the 12Z UKMET is more out of tolerance as it has an
upper low noted farther to the north of the model consensus
offshore of the Pacific Northwest, and also tends to now be more
progressive with the leading edge of height falls into the western
U.S.

Based on the latest model trends and clustering, a blend of the
12Z NAM/GFS/ECMWF solutions will be preferred at this time, and
this consensus is supported by the 12Z GEFS mean and 00Z ECENS
mean.


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

Orrison