Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1228 AM EDT Tue Jul 17 2018

Valid Jul 17/0000 UTC thru Jul 20/1200 UTC

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

12Z Model Evaluation...with Preliminary Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall Model Analysis for the CONUS...

Overall Preference: 00Z GFS; 12Z ECMWF; 12Z CMC Blend
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 00Z NAM and 12Z UKMET
are exhibiting the most significant differences from model
consensus, and have 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. On the flip side, the UKMET
concentrates most of its mid-upper level vorticity in the Upper
Midwest, resulting in a stronger cyclone there, and higher heights
along the East Coast relative to most ensemble members.

Therefore, the preference is for a blend of the GFS, ECMWF and
CMC, 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

Lamers