Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
135 AM EST Sun Feb 03 2019

Valid Feb 03/0000 UTC thru Feb 06/1200 UTC

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

00Z Model Evaluation...with preliminary Preferences and Confidence
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...Low pressure off the Southeast and Mid Atlantic Coast...
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Preference: General Model Blend
Confidence: Slightly Above Average

Short wave energy tracking from the Lower MS Valley across the
Southeast during Day 1 begins to close off as it reaches the NC
coast after 04/12Z. The 00Z Nam lags the consensus with the closed
low as it moves northeast after this time, while the 00Z GFS does
not show much of the closed circulation at any point through
06/12z. A surface low spins up in association with the mid level
system after 04/12Z, and initially, the 00Z NAM is a westerly
outlier with the low. However, the 00Z NAM joins the consensus
shortly thereafter, so a general model blend is preferred here,


...Short wave and surface low Northern Rockies into the Upper
Great Lakes...
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Preference: Close to the 00Z GFS
Confidence: Average

The 00Z NAM continues that model's solution of being the
easternmost outlier with the short wave energy tracking from the
Northern Rockies to the Northern Plains and Upper Great Lakes, and
the surface low that spins up ahead of it. The 12Z ECMWF continued
that model's solution of being slower than the consensus, but has
sped up its solution a bit in the past two runs. The 00Z has been
the most consistent with the timing of the short wave and the
track of the surface low. The timing differences appear to be due
in part to how the energy with the positively tilted long wave
trough over Alberta is handled. As might be expected, the 00z NAM
is faster with the long wave trough, and the 12Z ECMWF is slower.
Based on the above, the 00Z GFS remains the model of choice with
the short wave and surface system (which is close to the 18Z GEFS
mean as well). However, with spread remaining in the pattern,
confidence is average.


...Closed mid level low over CA/Great Basin...
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Preference: Non-00Z GFS blend
Confidence: Slightly above average

The 00Z NAM and 00Z GFS are close to the consensus with the strong
mid level low as it moves from the Pacific Northwest coast to a
position over northern CA by the end of Day 2. After that time,
the 00Z GFS becomes much faster with the mid level system as it
transitions from a closed low to a long trough, reaching the
southern Great Basin by 06/12Z. The faster speed of the 00Z GFS
with the trough seems to be tied to faster short wave energy west
of the British Columbia coast during late Day 2 into early Day 3.
The 00Z NAM remains closer to the consensus (including the 12Z
CMC/UKMET) throughout the transition, which is close to the 12Z
ECMWF/12Z ECMWF ensemble mean. Given the fairly tight clustering
(outside of the 00Z GFS) with respect to the mid level system,
forecast confidence is slightly above average.

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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