Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1249 PM EDT Tue Oct 23 2018

Valid Oct 23/1200 UTC thru Oct 27/0000 UTC

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

12Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of 00z ECMWF/UKMET, 12z GFS
Confidence: Average

Through the end of the week (27.00z), the synoptic pattern over
the CONUS is expected to feature longwave troughing over the
central/eastern US becoming more amplified while a ridge
develops/builds over southern California. Several impulses will
drop through the flow across the northern tier of the US (helping
to reinforce the troughing over the eastern 2/3 of the CONUS).

The biggest differences in the deterministic and ensemble guidance
lies across the central US with respect to a few shortwave
impulses dropping through Thursday and Friday. All of the models
have some sort of weak shortwave across the central Plains, but
varying degrees of magnitude and spatial placement through 25.12z.
The GFS/UKMET are further north with its axis compared to the
ECMWF/CMC, which is a bit weaker and further south. More
significant differences are noted as a stronger shortwave drops
out of Alberta into the northern Plains. The 12z GFS trended
faster and stronger with a closed low moving into the Dakotas by
the end of the period. This is in contrast to the ECMWF/UKMET
which bottles most of that energy in Canada. The 00z CMC does show
some resemblance to the 12z GFS, bringing a feature down into the
central Plains by 27.00z. This solution is in contrast to the 06z
GEFS, so it may be an outlier across that portions of the CONUS by
day 3.

For the surface low progged to develop along the Gulf Coast, there
is reasonable clustering of the deterministic models. The NAM is
further north with its low position, mostly inland across the Gulf
Coast states, while the GFS is furthest south, staying offshore
the longest. The UKMET/CMC/ECMWF are in good consensus and a blend
here would be a good proxy with all the available models.

With that all in mind, a blend of the 00z ECMWF/UKMET with
inclusion of the 12Z GFS (noting the stronger shortwave on day 3
in the northern Plains) seems appropriate for the CONUS for this
cycle.

...Hurricane Willa...
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Preference: non 00Z CMC blend closest to 15Z NHC advisory

Hurricane Willa will make landfall later today along the
west-central Mexico coast. In general, the latest 12z guidance
(GFS/NAM) didn't change much compared to the rest of the 00z
guidance. The official NHC advisory track lies well within a
consensus approach, outside of the 00z CMC which is too slow.
Please refer to the National Hurricane Center for the latest
information on the forecast for Hurricane Willa, as well as
discussion of model preferences and forecast reasoning.


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

Taylor