Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
143 AM EST Thu Jan 10 2019

Valid Jan 10/0000 UTC thru Jan 13/1200 UTC

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

00Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend with:
            - Greatest weight on 12Z EC ENS, 00Z ECMWF
            - Least weight on 00Z GFS
Confidence: Average

---06Z UPDATE---
The 00Z UKMET did converge toward the other deterministic models,
and thus a greater weight could be placed on it now. Otherwise,
there are no major changes to the model preference. No
deterministic model seems implausible, but the preference
generally leans in the direction of the ECMWF Ensemble Mean.

---PREVIOUS DISCUSSION---
An extension of the North Pacific Jet over the next few days
should lead to an amplification of the downstream pattern over the
East Pacific and North America. Such a shift in the pattern often
leads to noteworthy detail differences among the models, such as
with phasing of waves. That is the case with this forecast despite
some reasonably good agreement on the synoptic pattern and
large-scale QPF.

One area of concern is with the amplifying wave over the Plains on
Friday and Friday Night. A southern stream wave emerges from the
Four Corners region, but there are some additional low-amplitude
waves digging southeast from the Northern Rockies and Canadian
Prairies that should make an impact on the evolution of the trough
as it progresses to the East Coast. In general, the GFS seems less
inclined to consolidate the energy into a more robust vorticity
center over the Southern Plains around 12/00Z relative to the
other models. This led to a QPF pattern further south and more
dispersed than the other models, although the 00Z GFS has
continued a multi-run trend of nudging things slightly further
north. Given less model support for the GFS forecast, the
preference is to place less weight on the GFS, but not eliminate
it from the blend as it still is a plausible scenario. The
experimental FV3-GFS is closer to the ECMWF.

The 00Z GFS has also trended toward the ECMWF and ECMWF Ensemble
Mean (as well as the 00Z NAM) with the trough pushing onto the
West Coast on Friday Night. Given these trends, the preference is
to place the greatest weight overall on the ECMWF and EC ENS, with
less weight on the GFS for now. Less weight was also placed on the
UKMET due to limited model support. It has higher heights aloft in
the central and eastern CONUS after 12/00Z and also shows
significant differences from the other models with the height
pattern in the West by 13/12Z.


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

Lamers