Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
238 AM EDT Mon Sep 03 2018

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

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

00Z model evaluation...with latest preferences and confidence
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...Overall Synoptic Pattern across the CONUS...
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Preference: Blend of the 12Z ECMWF/12Z ECENS mean/00Z GEFS mean
Confidence: Average

The strong subtropical ridge over much of the Eastern U.S. will
remain in place going through Wednesday. Meanwhile, Meanwhile, the
mean layer upper trough over the Northwest U.S. should tend to
remain intact going through Tuesday, before then beginning to
weaken and shift eastward across southern Canada through Wednesday
and Thursday. In its place will be a building shortwave ridging as
deeper height falls evolve farther offshore of the Pacific
Northwest. Elsewhere, the weak trough over the Four Corners region
will tend to weaken further as heights regionally begin to come up
a bit, but the guidance agrees in maintaining at least a mid level
shear axis across the immediate central and southern High Plains.
On the larger scale, the model mass field differences are rather
small, but the 00Z CMC and to some extent the 00Z GFS are a little
faster than the model consensus with the wave activity lifting up
across the Midwest and toward the Upper Great Lakes region Tuesday
night and early Wednesday. The 00Z NAM and 00Z UKMET meanwhile are
a little slower overall by comparison, and actually the 00Z ECMWF
is close to the slower NAM/UKMET camp. The former 12Z run of the
ECMWF was a tad faster and has the best ensemble support relative
to the 00Z GEFS mean and 12Z ECENS mean over the Midwest, and so
will prefer to keep the former preference for the time being,
although the 00Z ECMWF appears perfectly fine across the remainder
of the CONUS.


...Potential Tropical Cyclone #7...
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Preference: Non-NCEP consensus...led by the 00Z ECMWF
Confidence: Slightly above average

Potential Tropical Cyclone #7 is forecast to move west-northwest
across the Florida Keys or the southern Florida peninsula early
this Monday morning, then cross the eastern Gulf of Mexico Monday
night before approaching the north-central Gulf Coast late Tuesday
or Tuesday night. Thereafter, the system will continue inland
across the lower MS Valley as it tracks around the southwest
periphery of the strong subtropical ridge over the Eastern U.S.
The latest global model consensus is in very good agreement on the
track heading which is in the vicinity of far southeast LA by 00Z
Wednesday. The 00Z NAM has finally trended toward the stronger
non-NCEP solutions with the idea of a relatively more organized
tropical cyclone, albeit perhaps a little slow as the system
approaches the north-central Gulf Coast. Meanwhile, the 00Z GFS
remains on the weak side of the dynamical model spectrum. Overall,
the non-NCEP guidance, and especially the 00Z ECMWF appear to have
the best handle on this system for the time being. In general, it
should be noted that the ECMWF has been the most consistent model
over the last couple of days regarding this system and its
evolution. Please consult the latest NHC public advisories and
discussions for more information on this system.


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

Orrison