Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1246 AM EDT Fri Oct 19 2018

Valid Oct 19/0000 UTC thru Oct 22/1200 UTC

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

00Z NAM/GFS evaluation...with preliminary preferences and
confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of the 00Z GFS/12Z ECMWF
Confidence: Slightly above average

The current synoptic setup featured a weakening shortwave trough
over Colorado with a stronger and amplifying shortwave over
south-central Canada. Shortwave ridging was located east of these
features over the Ohio Valley and Great lakes while strong ridging
was located over the Pacific Northwest coast with a developing
upper low off of the central California coast. A strong
sub-tropical ridge remains in place over the northern Gulf of
Mexico. Over the next 2-3 days, the pattern will evolve into mean
troughing over the northeastern quadrant of the U.S. with a few
shortwaves tracking through carrying reinforcing shorts of colder
air. Out West, a quasi-rex block will dominate the region with
only minor changes through Monday morning.

Differences are small regarding the synoptic scale features with
only minor timing/amplitude differences noted. However, the 00Z
NAM was noted to be stronger with mid-level vorticity coming out
of Mexico into western Texas on Saturday while the 12Z UKMET/CMC
were weaker. Thus, the middle ground 00Z GFS/12Z ECMWF are favored
here.

Out West, the ensemble means showed fairly good agreement with the
timing of a closed low expected to slowly nudge east Sunday into
Monday, with the 00Z NAM and 12Z CMC stronger or faster with the
12Z ECMWF/UKMET slightly slower. The 00Z GFS was similar in
magnitude and timing to the latest ensemble means.

Overall, a 00Z GFS/12Z ECMWF blend is preferred for the lower 48
from east to west.

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

Otto