Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
246 PM EDT Thu Aug 09 2018

Valid Aug 09/1200 UTC thru Aug 13/0000 UTC

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

12Z Model Evaluation with Preferences and Confidence
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...Overall Synoptic Pattern across the CONUS...
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Preference: Blend of 12Z GFS; 12Z UKMET; 12Z CMC
Confidence: Slightly below average

The global model ensembles have a fairly high degree of spread in
the mass fields by the end of the period (Sunday) over the central
and eastern CONUS. There are notable differences with the
placement of the trough over the Great Lakes and Northeast, as
well as a cutoff low developing over the Southern Plains.

The 12Z NAM is the most progressive with the northern trough, and
takes the trough axis as far east as the Hudson River by Sunday
afternoon, while the ECMWF closes off a low centered over western
Ohio. There is a spectrum of forecasts in between, but the global
models tend to be more clustered toward the ECMWF, and thus the
NAM is not preferred for this forecast. However, the 12Z GFS, CMC
and UKMET are in better agreement and not quite as far west as the
ECMWF. The preference is for the more consistent models, but the
ECMWF was considered and incorporated, just to a lesser extent.
The same preference existed for the southern Plains, with the new
ECMWF also further west with that cutoff low. The QPF trend in the
Texas area has been further south with new model runs, and thus
the WPC forecast trended in that direction as well.

Overall, confidence is slightly below average given the usually
good agreement in model mass fields during the summer months. The
spread is a little more than is typical, and there is also the
inherent uncertainty associated with more convectively driven
rainfall.

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

Lamers