Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
242 AM EDT Sun Oct 07 2018

Valid Oct 07/0000 UTC thru Oct 10/1200 UTC

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

00Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: 00Z ECMWF/12Z ECENS mean...thru 72 hrs
            00Z GFS/UKMET/ECMWF blend...after 72 hrs
Confidence: Slightly above average...thru 60 hours
            Slightly below average...after 60 hours

The guidance is in good agreement with the transition to a highly
amplified pattern across the CONUS which will be facilitated by a
very strong shortwave digging into the Southwest U.S. on Sunday.
The result will be a deep longwave trough over the Western U.S.
and a strong subtropical ridge across the Eastern U.S. going
through Tuesday. By Wednesday, the ridge across the Eastern U.S.
will begin to retreat eastward and allowing the height falls to
eject well out across the Plains and Midwest. The guidance though
agrees in maintaining a broad trough over the West though as
additional shortwave energy drops southward down from Southwest
Canada.
 
Regarding the details, the models agree very well with the deep
trough evolving over the Four Corners region through Monday and
Tuesday, but there remains some very meaningful differences with
the placement of the front across the Plains and Midwest, as the
00Z NAM is still displacing its front a tad farther south and east
versus the global model consensus. The global models are well
clustered with the portion of the front over the southern High
Plains, but farther north there remains spread as the 00Z GFS
still focuses its boundary northwest of the non-NCEP guidance
along an axis from eastern CO northeast up across the upper
Midwest. The 00Z ECMWF still overall has stronger support for a
solution essentially in between the NAM and GFS, which is favored
by the 00Z CMC/UKMET solutions and the 12Z ECENS mean. However, by
Tuesday night and Wednesday, the models all agree in shifting the
longwave trough east across the Plains and toward the Midwest
which will allow the front to advance east toward the MS Valley
and with low pressure lifting up across the upper Midwest.
Regarding the surface low by Wednesday, the ECMWF ends up on the
slow side of the model suite, with the GFS the fastest. The NAM
and CMC cluster in between the GFS and ECMWF, but the UKMET leans
toward the faster GFS.

Elsewhere across the CONUS, the guidance reloads the troughing
across the West by Wednesday as additional energy drops south from
British Columbia. The 00Z NAM is a strong outlier with the
additional energy . The 00Z GFS, 00Z UKMET and 00Z ECMWF are
better clustered with this system.
 
Based on the latest model spread and clustering of solutions
across the CONUS for this period, a blend of the 00Z ECMWF and 12Z
ECENS mean will be preferred through about 72 hours, with a blend
of the 00Z GFS, 00Z UKMET and 00Z ECMWF thereafter.


...PTC Fourteen...
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Preference: See the latest NHC forecast advisory

The guidance all agrees in taking PTC Fourteen northward across
the eastern Gulf of Mexico over the next 48 to 72 as a developing
tropical cyclone and with the system approaching or crossing the
northern Gulf Coast on Wednesday. The 00Z CMC takes the cyclone
farthest to the left with an impact more on the central Gulf
Coast. The 00Z NAM/GFS/UKMET solutions are clustered farther to
the east, with the GFS the faster solution of this camp.
Meanwhile, the 00Z ECMWF is left of the NAM/GFS/UKMET camp, but
not as far as the CMC solution and also the ECMWF is overall the
slowest solution in taking the system northward. Regarding the
ensemble means, the 12Z ECENS mean was taking the system a tad
east of the deterministic ECMWF with comparable timing. Meanwhile,
the 00Z GEFS mean is a tad left and slower versus the 00Z GFS. It
should be noted that most of the models, and especially the GFS
and UKMET are quite aggressive in deepening the cyclone. However,
the ensembles means as per the GEFS and ECENS means are notably
weaker which suggests a high degree of uncertainty regarding the
forecast intensity.

The 03Z NHC forecast track of PTC Fourteen is rather similar to
that of the GFS. Please consult the latest NHC forecast advisory
for more details on PTC Fourteen.


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

Orrison