Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
102 AM EDT Wed Oct 24 2018

Valid Oct 24/0000 UTC thru Oct 27/1200 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...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Overall Preference: Blend of 00Z GFS/12Z ECMWF/12Z UKMET
Confidence: Average

Anomalous mid-upper level ridging will build into the southwestern
U.S. through Friday night while quasi-zonal flow focuses north of
the ridge into the Pacific Northwest. Meanwhile, northern stream
troughing that is currently over the Northeast will slowly depart
the region through Friday but southern stream troughing currently
out West will amplify and slowly translate to just east of the
Mississippi River by Saturday morning as a number of shortwaves
traverse atop the western ridge through the Plains.

At the surface, two main cold fronts will have the greatest
influence on the sensible weather through Friday. A cold front
will reach the Pacific Northwest late today and stall temporarily
along the Washington coast until another surface wave moves
through sending the cold front into southern Oregon for Friday
night. The other front will develop as a surface low organizes
along an existing frontal boundary in the Gulf of Mexico. The
surface low is expected to hug the central Gulf Coast on Thursday
while tracking east before redeveloping along the southeastern
U.S. coast and tracking northward along the East Coast Friday
night into Saturday.

Regarding model differences, the ensembles are in decent agreement
and support the 00Z GFS, 12Z ECMWF and 12Z UKMET with the 00Z NAM
surface low nearly outside of the ensemble spread and 12Z CMC on
the southern edge. While moisture flux into the Pacific Northwest
may not differ all that greatly, staying closer to the 00Z GFS/12Z
UKMET/12Z ECMWF is preferred.

In the Gulf of Mexico, the 12Z CMC is slower/weaker with Hurricane
Willa along the Mexican coast with the other deterministic
guidance in good agreement with each other and observations at
00Z/24. The surface low track along the Gulf and East coast,
ensembles agree best with the 00Z GFS, 12Z ECMWF and 12Z UKMET.

In the northern Plains/south-central Canada on Friday, model
agreement with a closed low is poor, with only the 00Z NAM
appearing out of tolerance with the ensembles and remaining
deterministic models. Trends are inconclusive and the ensemble
means are between the 00Z GFS/12Z ECMWF/12Z UKMET (north) and 12Z
CMC (south). The preference is to go between the two for now but
confidence is reduced.


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

Otto