Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1151 PM EST Mon Dec 02 2019
Valid Dec 03/0000 UTC thru Dec 06/1200 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
ingest...
00Z Model Evaluation with Preferences and Confidence
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...Deep closed low impacting New England...
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Preference: General model blend
Confidence: Above average
Differences with the deep layer cyclone still impacting New
England are sufficiently minor that a general model blend can be
preferred as the system pulls away on Tuesday.
...Upper low offshore the West Coast through Tuesday...
...Energy then crossing the southern tier through Thursday...
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Preference: General model blend...through 36 hours
12Z ECMWF...after 36 hours
Confidence: Slightly above average
There is rather good agreement with the evolution of the upper low
offshore the West Coast through about 36 hours, but thereafter the
00Z GFS becomes a relatively progressive outlier solution (common
bias) as the energy traverses the southern tier of the nation
going through Wednesday and Thursday. The GFS is also a bit deeper
with surface low pressure that evolves across the southern Plains
and lower MS Valley through the period. On the flip side, the 12Z
CMC and 12Z UKMET overall are a little weaker than the model
consensus by the end of the period, with the 12Z ECMWF splitting
the difference between stronger and weaker camps. A general model
blend should be fine with this system through 36 hours, but a
preference toward the ECMWF is suggested thereafter with rather
solid support also from the latest GEFS mean and ECENS mean.
...Next amplifying trough across the OH Valley/Northeast...
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Preference: 00Z NAM/GFS and 12Z ECMWF blend
Confidence: Average
The models amplify a shortwave trough down across the OH Valley
and Northeast Tuesday and Wednesday. The 12Z UKMET and 12Z CMC are
a tad deeper than the remaining model consensus, with the latest
ensemble suite overall favoring the relatively weaker 00Z NAM/GFS
and 12Z ECMWF. Although it should be noted that there are some
GEFS members that do favor a deeper solution than this consensus.
For now, will lean toward the relatively more modest camp.
...Weak shortwave/low clipping the Northern Plains Wednesday...
...Crossing the Great Lakes on Thursday...
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Preference: Non-CMC blend
Confidence: Average
The models support a weak shortwave and associated surface
low/front clipping the northern Plains late Wednesday and quickly
reaching the Great Lakes region by late Thursday. The 00Z NAM/GFS
and 12Z UKMET solutions end up being more progressive with this
system and relatively flatter compared to the 12Z ECMWF and
especially the 12Z CMC. The ensemble means are a bit split with
the timing, as the GEFS is more progressive and the ECENS cluster
slower, but they all agree that the CMC is a deeper outlier. For
now, a compromise leaning toward a non-CMC blend is suggested.
...Deep closed low offshore the West Coast by Friday...
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Preference: Non-CMC blend...led by a 00Z GFS/12Z ECMWF blend
Confidence: Above average
The models support another very deep closed low evolving offshore
of the West Coast by Friday. The 12Z CMC is displaced a bit
northeast of the model consensus with its upper-level and surface
reflections. The majority cluster of solutions suggest a system
that will be a bit slower to advance east at the end of the
period, which is strongly suggest by the GEFS and ECENS clusters.
A non-CMC blend will be preferred with strong weighting toward a
00Z GFS/12Z ECMWF blend.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
Orrison