Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
145 AM EST Tue Feb 05 2019

Valid Feb 05/0000 UTC thru Feb 08/1200 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
Confidence: Average

The 00Z NAM/00Z GFS are close to the consensus concerning the
track of a closed mid level low over northern CA at the start of
Day 1, as it transitions from a closed low into a long wave trough
extending from the Northern Plains into the Southern Rockies at
07/12Z. After that time, the 00Z GFS slows and deepens a
developing closed mid level low over the Upper Great
Lakes/southeast Ontario, becoming the westernmost solution by
08/12z (as it has been for the past few cycles).

The 00Z ECMWF also slowed its timing with respect to the closing
mid level low as it crosses the Upper Great Lakes into Ontario.
The 00Z UKMET/CMC joined the slower solution group as well,
leaving the 00Z NAM as the easternmost solution with this feature.
The same is true with the track of the surface low, as the 00Z
ECMWF is closer to the 00Z GFS position after 08/00z (marking a
fairly significant shift to the west for the 00Z ECMWF when
compared to its previous two runs). Given the change in the 00Z
ECMWF solution, the 00Z GFS has been added back to the preferred
blend, and it would not be surprising to see the 00Z NAM come back
to the pack by slowing its mid level and surface systems in later
model runs.

The next closing mid level low south of the Gulf of Alaska drops
south, reaching a position west of the Northern CA coast by
08/12z. The 00Z NAM/00Z UKMET were a bit further west with the
closed low position by the time, but overall there is good
clustering with this feature, as well as its attendant surface
low. Because of the clustering, a general model blend is preferred
here with above average confidence.

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

Hayes