Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1229 PM EDT Fri Sep 06 2019

Valid Sep 06/1200 UTC thru Sep 10/0000 UTC

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

12Z Model Evaluation with Preferences and Forecast Confidence
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...Overall Pattern Across the CONUS...
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Preference: General model blend through Day 2; non-GFS northern
Plains Day 3
Confidence:

The initial 12Z guidance offers fairly good agreement through 48
hours across the CONUS. The main features of interest will
shortwaves across the northern tier, one of which will interact
with Hurricane Dorian as it becomes extratropical (more details
below). Another shortwave will push into the northern Plains on
Sunday where there is tight clustering between the models with
respect to the mass fields. Larger differences become apparent by
Day 3, mainly across the western U.S. and northern Plains with the
next (stronger) shortwave. With ridging upstream over the Upper
Midwest early next week, the next shortwave comes out of the
northern Rockies. The GFS is a flatter, more open solution that
subsequently is further east with its low position and QPF fields.
The other guidance members are more amplified with the shortwave,
with the low further west over Montana. Looking at the non-NCEP
guidance and the 06Z GEFS, it appears the 12Z GFS might be too
much of an outlier to include, especially for its QPF, at this
time. Otherwise, through Day 2, a general model blend can be
applied.


...Hurricane Dorian...
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Please refer to the official National Hurricane Center forecast
track. With the latest (15Z) NHC Advisory, there is good agreement
with the latest model suite through 48 hours as Dorian continues
northeast and begins extratropical transition, interacting with an
approaching shortwave trough from the Great Lakes region. A
multi-model consensus provides a good proxy for the official
track, with subtle differences seen in the latest models (GFS
west, NAM east) but overall there is tight clustering through 60
hours. 


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

Taylor