Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
135 AM EST Mon Feb 04 2019

Valid Feb 04/0000 UTC thru Feb 07/1200 UTC

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

00Z Model Evaluation...with Final Preferences and Confidence
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...Low pressure off the Carolina Coast...
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Preference: General Model Blend
Confidence: Slightly Above Average

The 00Z NAM was close to the model consensus with the track of the
closed low as it evolves into a long wave trough well east of the
mid Atlantic coast after 06/12Z. The 00Z GFS was a bit faster than
the consensus with the speed of the mid level system and attendant
surface low, though there is still a fair amount of spread in the
strength of the surface low as it tracks northeast. The 00Z ECMWF
remains several millibars deeper than other guidance, especially
after 05/12Z, even as its surface position is close to the loosely
clustered consensus. At this point, a general blend is preferred,
as the impacts of this system over land after Day 1 should be
minimal.


...Short wave and surface low crossing the Upper Great Lakes into
Northern New England...
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Preference: General Model Blend
Confidence: Average

The 00Z NAM and 00Z GFS are close to the consensus with the track
of the mid level system, as it moves from the Upper Great Lakes
across Ontario and the rooftop of ME, though the 00Z GFS becomes
faster with the short wave as it moves over New Brunswick after
06/00Z. Both the 00Z NAM and 00Z GFS are close to the consensus
with the surface low through 07/12Z. While there are some minor
differences in the strength of the surface low, there is enough
clustering to use a general model blend for the preference.


...Mid level system tracking from the West Coast into the Northern
Plains
and Southern Rockies...
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Preference: 00Z NAM/00Z ECMWF blend
Confidence: Below Average

Both the 00Z NAM/00Z GFS are close to the consensus as a strong
closed mid level low drops south from the Pacific Northwest coast
to a position over Northern CA at 06/12Z. After that time, the 00Z
GFS becomes faster than the consensus as the closed low evolves
into a long wave trough crossing the Rockies toward 07/12Z. The
faster mid level solution of the 00Z GFS results in its surface
low being displaced further north into the IL/WI. The 00Z NAM/00Z
ECMWF keep weaker surface lows closer to a frontal boundary
extending from the Southern Plains into the Mid Atlantic states.
Since the 00Z GFS surface low position was much further north than
the consensus (including its past few cycles and the 00Z GEFS
mean), if was not included in the preference.

The 00Z NAM/00Z ECMWF constituted a tenuous consensus with the
track of the surface low, though there were some issues with
placement and strength. Given the spread in the guidance
concerning the placement and strength of the surface low (and to a
lesser degree, the mid level trough), the abovementioned model
blend was used as the preference. However, the large spread in
place has resulted in below 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

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