Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
244 AM EDT Wed Sep 05 2018

Valid Sep 05/0000 UTC thru Sep 08/1200 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 00Z GFS/00Z ECMWF
Confidence: Slightly above average
 
The model mass field differences were fairly small over the next
several days across the CONUS, and individual deterministic models
are contained well within the total envelope of ensemble spread.
Although the 00Z NAM and 00Z CMC are a bit stronger with the mid
level trough over the central Plains on Friday and Saturday which
plays a role with the track of T.S. Gordon. The stronger NAM pulls
Gordon farther north across the middle MS Valley, and the CMC
which is stronger and more progressive compared to the model
consensus allows Gordon to recurve faster off to the northeast and
closer to the lower OH Valley. The guidance is otherwise in good
agreement across the Western U.S. with the arrival of the next
upper trough, and also the troughing coming across the Great Lakes
and into the Northeast by this weekend. The 00Z GFS and 00Z ECMWF
are very well clustered overall, and based on this along with
agreement with the latest ensemble means, a GFS/ECMWF blend will
be preferred across the CONUS.


...Tropical Storm Gordon...
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Preference: Please consult the latest NHC forecast
 
The 00Z GFS and 00Z ECMWF as a consensus is closest to the 03Z NHC
forecast track for Gordon out through 72 hours, with the 00Z NAM
gradually pulling Gordon a bit more quickly to the north by the
end of the period toward the middle MS Valley. The 00Z CMC
meanwhile is rather close to the NHC track through about 48 hours,
but then is quickest to recurve Gordon off to the northeast and
toward the lower OH Valley thereafter. The 00Z UKMET gradually
shifts the track of Gordon a bit left of the NHC track by 72
hours. All of the models though agree in slowing Gordon down
between 36 and 72 hours as it approaches an upper trough over the
Plains and then begins to round the western periphery of the
subtropical ridge over the Eastern U.S. At this time, the
GFS/ECMWF cluster is closest to the NHC track. Please consult the
latest NHC forecast advisories and discussions for more details on
Gordon.


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

Orrison