Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
232 AM EDT Mon Jul 13 2020
Valid Jul 13/0000 UTC thru Jul 16/1200 UTC
...See NOUS42 KWNO (ADMSDM) for the status of the upper air
ingest...
00Z Model Evaluation with Final 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
...07Z update...
The 00Z ECMWF/UKMET nudged faster with the shortwave exiting the
Northeast on Tuesday/Tuesday night compared to their previous 12Z
cycles, so differences have shrunk while continuing to support a
general model blend.
Trends over the past 24 hours have been faster to exit a mid-level
vorticity max/closed low over New England toward the east on
Tuesday. The 12Z ECMWF/UKMET are a little slower than the
remaining deterministic consensus and the latest ensemble means.
Differences are relatively minor and so a general model blend will
work fine, but perhaps less weight should be given to the slower
12Z ECMWF/UKMET.
...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 CMC blend
Confidence: Average
...07Z update...
The 00Z ECMWF/UKMET/CMC did not make significant changes compared
to their previous 12Z cycles.
The models show good overall agreement with a broad 500 mb trough
and associated surface cold front moving across the central to
northern Plains today and Monday night. Some minor timing and
amplitude differences continue to be seen, with the 00Z GFS a bit
faster with mid-level height falls across the Northern Tier.
For the surface front, the 00Z NAM and 00Z GFS were noted to be
faster with the progression of the front through the Southern
Plains on Tuesday, but the 12Z UKMET was much slower with the 12Z
ECMWF/CMC in between the two camps. The faster timing might work
out as often the models can be slow to push the cooler air
southward through the High Plains, but the faster 00Z NAM
progression with a frontal wave through the Midwest on Wednesday
is where the 00Z NAM loses out on being preferred.
Overall, model differences are small, but leaning on a 00Z GFS,
12Z ECMWF and 12Z CMC blend is considered best at this time.
...Cut off low west of California by Thursday morning...
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Preference: General model blend
Confidence: Average
...07Z update...
The 00Z ECMWF/UKMET/CMC did not make significant changes compared
to their previous 12Z cycles.
Good model agreement exists with a 700-500 mb low closing off by
mid-week from a weak and nearly stationary trough axis in place
over the western U.S. today. The latest guidance shows very little
in the way of differences with the timing, placement and strength
of this feature. Therefore, a general model blend will be used for
the preference.
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