Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1120 PM EST Mon Feb 04 2019

Valid Feb 05/0000 UTC thru Feb 08/1200 UTC

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

00Z NAM/GFS Evaluation...with Preferences and Confidence
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...Overall pattern across the CONUS...
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Preference: General model blend (except a non-GFS blend over the
Upper Great Lakes)
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).

This difference is reflected in the placement of the surface low
that tracks from the Central Plains into western Quebec during
Days 2 and 3. The 00Z NAM is closer to the 12Z ECMWF with the
track of the surface low, and this position is supported by the
12Z UKMET/CMC. Not surprisingly, the 18Z GEFS mean members support
the more western solution with the mid level and surface systems,
while the 12Z ECMWF ensemble members support the eastward position
of the 00Z NAM/12Z ECMWF. At this point, a non-GFS blend is
preferred based on the above, though confidence is average, based
on the amount of spread in the ECMWF ensemble/GEFS surface lows.

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/12Z 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