Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
237 PM EDT Thu Jun 28 2018

Valid Jun 28/1200 UTC thru Jul 02/0000 UTC

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

12Z model evaluation...including final preferences and confidence
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...Western US to the Northern Plains and Upper Great Lakes...
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Preference: 12Z NAM/12Z ECMWF/12Z GEFS mean blend
Confidence: Average

The 12z NAM remains close to the consensus as it tracks the long
wave trough from the West Coast to the Rockies by Sat morning.
After that time, the 12Z NAM slows its pace with the trough as its
wavelength shortens over the Northern Plains into the Upper Great
Lakes by Mon afternoon. Initially, 12Z GFS is close to the
consensus with the long wave trough, but it becomes slower and
deeper with the trough Sat night, remaining slower and deeper as
it approaches the Upper Great Lakes Mon.

The 12z GFS is much slower than the 06z GFS, as well as the 12Z
GEFS mean. Based on this, the 12z GFS was not included in the
preference for this system. The 12Z ECMWF/00Z ECMWF ensemble mean
were closer to the 12Z GEFS with the mid level system, as well as
its surface low. Based on the consistency of the the ECMWF and the
GEFS, these models were included in the preference. Since the 12Z
NAM is close to the middle ground between the faster ECMWF/slower
GFS, it was included in the preference as well.


...Eastern US...
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Preference: General model blend
Confidence: Above average

The 12Z NAM and the 12z GFS were close to the consensus with the
negatively tilted long wave trough weakening as it moves northeast
across the Canadian Maritimes. Otherwise, there was very good
agreement with the placement and strength of the developing mid
level ridge over the Lower Ohio Valley Fri, which shifts to the
Northeast/Mid Atlantic Sat into Sun. The 12Z UKMET remains the
furthest west with the ridge axis, but not far enough away from
the consensus to leave it out of the general model blend.


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

Hayes