Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1231 AM EDT Fri Sep 21 2018

Valid Sep 21/0000 UTC thru Sep 24/1200 UTC

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

00Z Model Evaluation...with Preferences and Forecast Confidence
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...Overall preference for the entire CONUS...
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Preference: Blend of 12Z ECMWF, 12Z UKMET, 00Z NAM
Confidence: Average

Over the first 36 hours of the forecast, model differences are
very minor in the northern stream closer to the Canadian border,
with relatively zonal flow. The greater differences initially are
with a trough that will evolve over the Southern Plains. The 00Z
GFS continues to shear out the mid-upper level vorticity and
deamplify the trough faster than all the other deterministic
models, which has been the case in prior runs. It is worth noting
that it also deamplifies the trough faster than almost all its
ensemble members (18Z GEFS). Given the lack of support, the
preference is to lean toward the broader consensus, as this will
have implications on QPF. Over the past 5-6 model runs, the GFS
has trended in the direction of the consensus, but still remains
quite different.

After this initial part of the forecast period, a trough will
amplify over the West. The 12Z CMC and 00Z GFS offer substantial
differences from the model consensus. The GFS is a bit closer, but
is on the faster end of model spread. However, the CMC is much
more amplified and slower than the other models, eventually
closing off an upper level low over California. The preference is
to lean in the direction of the more consistent ECMWF, NAM and
UKMET.


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

Lamers