Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
238 PM EDT Thu Oct 18 2018

Valid Oct 18/1200 UTC thru Oct 22/0000 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: Blend of the 12z GFS/12z ECMWF, with more weight
toward the 12z ECMWF
Confidence: Slightly above average

19z Update: The 12z ECMWF along with the 12z CMC/UKMET were fairly
similar to the 12z GFS/NAM through 36 hours, then begin differing
with respect to the shortwave trough coming into the Upper Midwest
by Saturday. The ECMWF was the strongest solution, closing off at
500 mb and is slower compared to the GFS/NAM. The CMC/UKMET were
more similar to the ECMWF with its placement, but showed similar
strength as the GFS. The GFS is the fastest solution through the
whole evolution of the trough swinging through the Northeast US
into Sunday.

So the preference continues with a compromise between the 12z GFS
and 12z ECMWF, with some additional weight toward the ECMWF given
its similarity with the UKMET/CMC and the ensemble means.

---Previous Discussion---
The current synoptic setup features a weakening shortwave trough
over Utah with another stronger shortwave over Nova Scotia. The
subtropical ridge remains shunted south across southern Florida to
the southern Texas Gulf Coast. A quasi-rex block is across the
eastern Pacific along the US West Coast. Over the next few days,
the Utah shortwave lifts northeast, phasing with another piece of
energy dropping south out of central Canada. This will carve out a
deep trough over the Great Lakes into the eastern US with
mid-level ridging continuing through the Intermountain West. At
the surface, a strong cold front will sweep across the
central/eastern US with sprawling Canadian high pressure in its
wake bringing a reinforcing shot of cooler air.

There were no major differences in the synoptic pattern with the
12z GFS/NAM compared to the 00z model cycles. The GFS was a bit
faster with the trough progression compared to the 00z ECMWF.
Overall given the consistent agreement with the features through
the weekend, a blend of the 12z GFS and 00z ECMWF, weighted
slightly more toward the 00z ECMWF, is preferred.

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

Taylor