Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1231 PM EDT Sat Aug 11 2018
Valid Aug 11/1200 UTC thru Aug 15/0000 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
12Z Model Evaluation with Preferences and Confidence
...Overall Synoptic Pattern across the CONUS...
Preference: General model blend; weighted most toward the 00Z ECMWF
Ensemble mean and 12Z GFS
The trough over the Northeast will persist through the next few
days, while a ridge over the interior West begins to break down
into a series of shortwave troughs embedded in weak zonal flow.
Models do show some differences, particularly as the ridge begins
to break down. However, in general, all the deterministic models'
forecast mass fields are contained well within the ensemble
spread. Notable exceptions include the 12Z NAM (displaced east
with the trough axis in the Northeast by Tuesday) and 00Z
CMC/UKMET (more substantial ridging on either side of the
Northeast trough relative to most ensemble members). The 12Z NAM
and 00Z ECMWF also show a weaker shortwave trough over the Pacific
Northwest by Tuesday, and a much stronger shortwave trough over
the Northern Plains. While these can't be ruled out, they lack the
ensemble support that the GFS, CMC, and UKMET have. The ECMWF
Ensemble mean, for instance, is closer to the GFS on Tuesday in
the northern tier of states.
Given the broad model agreement and similarity in the QPFs, the
preference is for a broad model blend. However, greater weight
will be given to the 00Z ECMWF Ensemble mean and 00Z GFS, as they
have better ensemble support for some of the shortwaves that
evolve over the northern CONUS.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml