Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1125 AM EST Sat Nov 24 2018

Valid Nov 24/1200 UTC thru Nov 28/0000 UTC

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

12Z Model Evaluation...with Final Preferences and Confidence
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...Overall pattern across the CONUS...
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Preference: General model blend, weighted most 12Z GFS, 00Z CMC
Confidence: Slightly above average

There is better clustering of deterministic models with the
arrival of the 12Z NAM and GFS today, and the 12Z GFS is
relatively close to the ensemble means in many respects. This
increases confidence in the forecast; better clustering with an
amplified pattern should yield more predictability in general.
However, mesoscale details will still make a big impact with
several systems.

From the synoptic perspective, however, the model preference is to
go with a general model blend as the model similarity has improved
and the deterministic model mass fields are generally contained
within the full envelope of ensemble spread. Greater weight was
given to the 12Z GFS and 00Z CMC given their close approximation
of the ensemble means.

For example, with the developing low in the Midwest and Great
Lakes, the 12Z NAM continues to be on the fast end of model
spread, while the 00Z ECMWF was on the slow end. The GFS and CMC
were roughly in the middle with respect to timing, and reasonably
represent a large cluster of model forecasts.

On the coast of the Northeast US, the NAM and 00Z UKMET showed
surface low development well offshore, while the CMC, ECMWF and
GFS were more closely clustered near the coast (and were much
closer to the ensemble means). The expectation is that surface low
development would be most likely close to the coastline with a
negatively tilted wave aloft that should stay mostly inland.

On the West Coast, there does seem to be some slight differences
with respect to timing of the next wave that will arrive, but a
general model blend should represent a reasonable consensus
forecast for now.


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

Lamers