Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
237 AM EDT Sat Aug 18 2018

Valid Aug 18/0000 UTC thru Aug 21/1200 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 Synoptic Pattern across the CONUS...
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Preference: Blend of 00Z GFS, 12Z ECMWF, 12Z ECMWF Ensemble Mean
Confidence: Average

---06Z UPDATE---
The 00Z ECMWF has trended closer to the GFS with the developing
low in the Midwest, so there is no change in the preference --
leaning toward a blend of the GFS and ECMWF. The other models
continue to show greater differences.

---PREVIOUS DISCUSSION---
Over the next few days, the primary forecast concern as it relates
to QPF will be the evolving low pressure system over the central
Plains and Midwest. Therefore, the model preference is most
strongly related to that system, as QPF in other regions is more
limited. After the initial formation of the surface low near
Kansas City late on Sunday, there is a spread with how quickly the
low ejects to the northeast. The preference is for a blend of the
GFS and ECMWF, as that would put the surface low position very
close to the ECMWF Ensemble Mean (in the middle of the model
spread), and the two models are quite close with their handling of
the upper level pattern.

The 00Z NAM and 12Z UKMET are a bit out of phase with the trough
aloft, shifting it further east, and showing different amplitudes.
They also exhibit greater differences, along with the 12Z CMC,
with the evolution of the upper level pattern over the West by
Monday, showing considerable differences from the ensemble means
and the GFS and ECMWF.


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

Lamers