Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1224 AM EDT Sat May 19 2018

Valid May 19/0000 UTC thru May 22/1200 UTC

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

00Z model evaluation...with preferences and confidence
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...Broad upper trough and embedded MCVs over the Southeast...
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Preference: General model blend
Confidence: Above average

The models are in good agreement with the larger scale details of
this energy as it ejects out of the Southeast and crosses the OH
Valley, Mid-Atlantic and southern New England through Saturday. A
general model blend will be preferred.


...Upper trough crossing the upper Midwest this weekend...
...Cold front/surface wave crossing the region...
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Preference: General model blend
Confidence: Above average

The latest guidance has finally come into rather good agreement
with this system, and thus a general model blend will be preferred.


...Upper trough/closed low over the Four Corners...
...Ejecting east across the central Plains this weekend...
...Crossing the Midwest by Monday...
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Preference: Blend of the 00Z GFS and 12Z ECMWF
Confidence: Average

Ensemble spread has decreased from yesterday, and the guidance is
gradually coming around toward a better consensus on the evolution
of the upper trough/closed low energy ejecting across the Four
Corners region currently. All of the guidance takes this energy
out across the central Plains through the weekend and then the
Midwest going through Monday. The 00Z NAM still looks a little too
deep on Saturday as the energy crosses the High Plains. Although
it tends to come in closer to the model consensus by Sunday. The
12Z CMC however eventually looks a little too deep by later Sunday
and Monday as the energy arrives toward the Midwest. This results
in the CMC having a somewhat deeper and slower surface low as
well. The 00Z GFS, 12Z UKMET and 12Z ECMWF are a bit weaker by
comparison, although the UKMET surface wave evolution appears to
be a little slow and deep as it crosses the central Plains through
Saturday and Sunday. The better model clustering is closer to the
GFS and ECMWF solutions and so a blend of these models will be
preferred now.


...Upper trough digging into the West on Sunday...
...Closed low digging into the Southwest Monday and Tuesday...
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Preference: General model blend
Confidence: Above average

The models show good agreement with this system through the period
as the height falls arriving across the West ultimately lead to a
closed low over the Southwest by Tuesday. Will prefer a general
model blend.


...Mid level trough developing over the eastern Gulf of Mexico by
Sunday...
...Lifting up across the Southeast on Monday...
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Preference: Blend of the 00Z NAM, 00Z CMC and 12Z ECMWF
Confidence: Average

The models develop a weak mid level trough and possible closed low
over the eastern Gulf of Mexico by late Sunday which then lifts up
across the Southeast on Monday. The 12Z UKMET takes this system
farthest west and is an outlier. Overall, the 00Z GFS is the most
developed/strongest with this system and also has a fairly
well-defined surface low which the UKMET also has. The remaining
guidance including the 00Z NAM, 12Z ECMWF and 12Z CMC are all
weaker with basically a surface trough. There is not much support
for anything more than a surface trough with this system when
looking at the latest ensemble plots, including both GEFS and
ECENS suites. So, will lean toward the weaker consensus at this
time.


Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml

Orrison