Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
103 AM EDT Mon Oct 22 2018

Valid Oct 22/0000 UTC thru Oct 25/1200 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: 00Z GFS / 12Z ECMWF blend
Confidence: Average

In general, the synoptic pattern across the CONUS through
Wednesday night will be characterized by troughing over the Great
Lakes, Northeast and Mid-Atlantic while a ridge across potions of
the western U.S. breaks down with the approach of a shortwave
trough in the Northwest. Eventually the remnants of Hurricane
Willa will spread into the southern U.S. (see section below).

Trends and the latest ensemble means are agreeable toward a 00Z
GFS / 12Z ECMWF blend across the entire lower 48. Across the
Northeast, upper troughing will move across the region on Tuesday
helping to spawn surface low redevelopment off of the coast of
Maine Tuesday night. Only the 12Z CMC significant differs here.

Elsewhere, there are timing differences across the Northwest with
a progressive upper trough and into the southern Plains with a
trough that is currently over southern California. The 00Z GFS and
12Z ECMWF fit the middle of the spread here and agree with the
ensemble means. See below regarding the 00Z NAM and its faster
forecast with the remnants of Hurricane Willa, but also worth
noting is that the 00Z NAM is the farthest north with a surface
low along the western Gulf coast on Tuesday into Wednesday.

...Hurricane Willa...
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Preference: 00Z GFS/12Z ECMWF blend closest to 03Z NHC advisory
Confidence: See NHC products

The 00Z NAM is fastest while 12Z UKMET/CMC slowest relative to the
03Z NHC advisory for Willa. A blend of the 00Z GFS and 12Z ECMWF
has the best agreement with the NHC 03Z advisory with the 12Z
ECMWF on the slower side. For the latest information on Tropical
Storm Willa, see the official NHC advisory.

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

Otto