Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1259 AM EDT Tue Jul 14 2020
Valid Jul 14/0000 UTC thru Jul 17/1200 UTC
...See NOUS42 KWNO (ADMSDM) for the status of the upper air
ingest...
00Z NAM/GFS Evaluation with Preliminary Preferences/Confidence
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...Mid-level shortwave troughing over the northeastern quarter of
the U.S. Monday to Wednesday...
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Preference: General model blend
Confidence: Average
The models show similarly with this system. Any differences, which
correspond to a departing offshore surface low located east of
Nova Scotia, appear once this system's impacts have left the
Northeast. Therefore, a general model blend can be used.
...Longwave trough axis moving through the north-central U.S.
through Wednesday with accompanying surface cold front...
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Preference: 00Z GFS, 12Z ECMWF, 12Z UKMET blend
Confidence: Average
As a large closed low and associated longwave trough axis track
eastward across southern Canada through the rest of the week, a
corresponding cold front will move into the Great Lakes and Great
Plains. While the 00Z GFS was noted to be a little fast Wednesday
afternoon, the most significant difference relates to a shortwave
tracking through the base of the trough Wednesday into Thursday
morning, over the Great Lakes. The 00Z NAM and 12Z CMC are
stronger with this feature and show up as strong minorities
compared to the ECMWF/GEFS and CMC ensemble members valid 12Z/16.
At the surface, both the 00Z NAM and 12Z CMC depict a stronger
surface wave along the front moving into the Great Lakes Wednesday
night into Thursday. The 00Z GFS, 12Z ECMWF and 12Z UKMET are in
reasonable agreement to each other and the agreeable ensemble
means, hence the preference will follow suit.
...Cut off low west of California by Thursday morning and
progressive trough crossing the Pacific Northwest...
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Preference: General model blend
Confidence: Average
The latest models continue to show good agreement with a 700-500
mb low closing off by mid-week over the western U.S. and
retrograding offshore of California by late in the day Wednesday.
There is also good agreement, albeit minor amplitude differences,
with a progressive mid-level trough axis into the Northwest on
Thursday. A general model blend represents both systems along the
West Coast well.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml
This product will terminate August 15, 2020:
www.weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination.
pdf
Otto