Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1257 AM EDT Sun Oct 21 2018

Valid Oct 21/0000 UTC thru Oct 24/1200 UTC

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

00Z NAM/GFS evaluation...with preliminary preferences and
confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall Pattern Across the CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: 00Z GFS / 12Z ECMWF blend
Confidence: Slightly above average

The synoptic pattern across the CONUS through Wednesday morning
will feature mean mid-upper level troughing over the northeastern
quadrant of the U.S. with the breaking down of a rex block along
the West Coast as an upper trough axis swings across on Tuesday.
The departure of a sharp upper trough along the East Coast this
morning will be replaced with a broader trough across the Great
Lakes/Northeast Tuesday evening. Out West, a slow moving upper
trough/closed low will translate eastward from California today
toward the Four Corners region Tuesday night.

Across the Northeast, there is generally good agreement with the
mid to lower levels but the 00Z NAM, 00Z GFS and 12Z ECMWF match
closest to the latest ensemble means.

Across the Southwest into Texas, trends have shown convergence
with the timing of a trough axis slowly moving east, but the 00Z
NAM is significantly faster with Tropical Storm Willa and
associated moisture (see below section) which may have impacts on
rainfall across portions of New Mexico.

Out West, there is good agreement throughout except for the 12z
ECMWF which is a bit slower with a cold front nearing the West
Coast on Tuesday, mainly west of northern California. However, the
differences over land are small enough that the ECMWF can be
included as part of a general blend.

A 00Z GFS/12Z ECMWF blend can be used from the West Coast to the
East Coast through Wednesday morning.

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

The 00Z NAM is considerably faster with Willa and its remnants as
the system makes landfall in western Mexico. Meanwhile, the 12Z
UKMET/CMC are much slower and west than NHC. A blend of the 00Z
GFS and 12Z ECMWF appears closest to the latest (03Z) NHC advisory
for Willa but the GFS is a bit faster and the ECMWF a bit slower.
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