Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1248 PM EDT Tue Jul 17 2018

Valid Jul 17/1200 UTC thru Jul 21/0000 UTC

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

12Z Initial Model Evaluation...with Preliminary Preferences and
Confidence
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...Overall Model Analysis for the CONUS...

Overall Preference: 12Z GFS/00Z ECMWF compromise
General Confidence: Average

Models are in good agreement through Wednesday, but then greater
differences begin to evolve with a trough moving through the
northern Plains and into the Upper Midwest, and how the pattern
evolves downstream over the Eastern US. The 12Z NAM is exhibiting
the most significant differences from model consensus, and has
been discounted from the preference. The NAM carries more
mid-upper level vorticity into the Southeast and this results in
more amplification to the broad downstream trough over the region.
Its heights aloft are generally lower than most NAEFS and ECMWF
ensemble members.

Therefore, the preference is for a blend of the GFS and ECMWF,
which show reasonably good agreement and are closest to the
available ensemble means. Forecast confidence is only rated as
average, as the model differences are a little more notable than
in recent weeks. Most uncertainty is in the eastern half of the
country, with higher confidence (given better mass field
agreement) in the West.


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

Hamrick/Lamers