Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1233 PM EDT Mon May 14 2018

Valid May 14/1200 UTC thru May 18/0000 UTC

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

12Z Model Evaluation...with Preliminary Preferences and Confidence
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Overall Preference: Blend of 12Z GFS, 00Z ECMWF, 00Z UKMET
Overall Confidence: Slightly Above Average

No significant initialization errors were noted. The overall
preference across the CONUS for the next several days is a blend
of the 12Z GFS, 00Z ECMWF, and 00Z UKMET. All three of these
models seemed to be relatively consistent with ensemble means, and
did not show large differences with most of the systems across the
country.

The most notable difference with the 12Z GFS was a more amplified
trough over the Gulf of Mexico with the 582 dkm isoheight at 500mb
about 400km south of the consensus of the other models and the
ECMWF Ensemble mean. However, this does not seem to substantially
affect the sensible weather. The GFS also shows much stronger
mid-upper level vorticity maxima associated with convective
clusters initiating in the Plains. This does seem to affect its
precipitation forecasts, so caution is advised with the GFS in
that region. However, overall the 12Z GFS seems to be reasonably
close to the UKMET and ECMWF in most respects.

Regarding the other models: the 12Z NAM has a more potent and
amplified trough in the Upper Midwest by Wednesday Night and
Thursday, and the 00Z CMC shows a much stronger (nearly
stationary) vort max near northeast Wyoming and spreads the
western trough further east than the other models. These
differences do seem to substantially affect near-surface and
sensible weather fields in the model forecasts, so the preference
was to lean away from the CMC and NAM at this time.

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

Lamers