Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
219 PM EDT Fri Oct 19 2018

Valid Oct 19/1200 UTC thru Oct 23/0000 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/ECMWF/UKMET
Confidence: Slightly above average

19z Update: The 12z UKMET/CMC came in very similar in the large
scale pattern through 60 hours (22.00z) compared to the 12z
GFS/NAM. With the shortwave dropping in across the Upper Midwest
Monday, the UKMET is flatter and faster compared to the other
deterministic. For the Western US and BC, the UKMET came in
stronger (similar to the 00z CMC). Overall, confidence in that
area of the forecast domain is lower with larger model spread
compared to the rest of the CONUS.

---Previous Discussion---
The current synoptic setup featured a quasi-rex block over the
western US with downstream troughing over the central/eastern US.
Over the next 24 hours, a shortwave dropping out of Canada will
carve out a deeper trough over the Great Lakes and Northeast US,
driving a surface cold front south and east. In its wake, strong
Canadian high pressure will reinforce seasonably cool air across
the central/eastern US.

In general, the 12z GFS/NAM showed little differences in heights
through the weekend compared to previous runs and other
deterministic models. The GFS (and NAM to some degree) is faster
with the shortwave trough progression across the Great Lakes
region through Saturday compared to the 00z ECMWF/CMC/UKMET. But
it is now more aligned with the 06z GEFS mean. There's very little
difference at the surface with the frontal passage through
Saturday night.

Out West, by early next week a closed low will approach the BC
coast where the models exhibit some magnitude and timing
differences. The 00z CMC is stronger (closing off 522 at 500 mb)
compared to the ECMWF/GFS which is more open, elongated, and
slower. With the ridging expected across the Intermountain West,
would lean toward a slower progression by that period.

The 12z NAM followed its previous run and is the strongest for a
lobe of vorticity coming out of Mexico into west central Texas by
Saturday evening. The other deterministic models are in good
agreement with placement and magnitude there.

Overall, a general blend of the 12z GFS with the 00z ECMWF/UKMET
is preferred for the CONUS.

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

Taylor