Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
154 AM EST Sun Nov 11 2018

Valid Nov 11/0000 UTC thru Nov 14/1200 UTC

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

00Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: General Model Blend...Day 1
            Blend of the 00Z GFS/UKMET/ECMWF...Day 2/3
Confidence: Average

The upper level flow across the CONUS initially features a deep
layer ridge just off the West Coast with a downstream longwave
trough across the central U.S. Meanwhile, a deep closed low is
seen exiting northeast and away from the Northeast and up across
Quebec as flat zonal flow is noted farther south across the
southern tier of the nation. Over the next 36 to 48 hours, the
deep layer ridge off the West Coast will shift east into the
Western U.S. as a deep closed low advances into the Gulf of AK.
Multiple shortwave impulses will be dropping down the east side of
the ridge as it moves east and this will lead to a much more
amplified pattern downstream with an amplifying trough across the
central and southern High Plains Sunday and Monday which then
gradually advances east across the lower MS Valley on Tuesday.
Meanwhile, the guidance shows a bit of stream separation with
time, and by Monday and Tuesday there will be a more pronounced
northern stream trough digging across the upper Midwest and Great
Lakes region. Surface low pressure will develop over the western
Gulf of Mexico by early Monday in response to the energy digging
across the southern Plains and lower MS Valley and will lift
northeast and up across the interior of the Southeast through
Monday night. Secondary low pressure that will be more tied into
the amplifying northern stream trough over the Midwest and Great
Lakes is expected to form along a coastal front by early Tuesday
near the Mid-Atlantic coast and then lift north across southern
and eastern New England Tuesday night and across Atlantic Canada
on Wednesday. Elsewhere, by the end of the period, the ridge over
the western U.S. will have broken down and there should be a
shortwave coming into the Pacific Northwest by that time as
supported strongly by all of the models.

The model mass field spread is rather minimal through early
Monday, although the 00Z NAM begins to amplify the upper trough
digging across the Four Corners region and southern High Plains a
bit more aggressively than the global models by that point.
Thereafter, the NAM goes on to become a bit of a slower outlier
with the evolution of the southern stream energy/troughing.
However, it should be noted that the 00Z non-NCEP solutions
involving the UKMET/CMC and ECMWF have all trended slower and
deeper with this energy and they all support a closed low
evolution over the southern Plains through Tuesday and Wednesday
like the NAM except they are farther east. The CMC overall is now
the deepest solution by the end of the period. The 00Z GFS is the
most progressive with this energy and still supports a bit more of
an elongated and positively tilted trough cutting across the lower
MS and TN Valleys through Tuesday and Wednesday. The NAM along the
East Coast also has a surface low that develops faster and lifts
quicker up toward southern New England by Tuesday. The global
models are a bit slower with the low evolution through Tuesday,
but then converge toward a solution that is closer to the NAM by
early Wednesday. Also, the global models collectively have trended
a little farther east with the low track and support a bit more of
a coastal track versus one that is inland over eastern New
England.

Based on the latest model trends, and clustering of deterministic
and ensemble solutions, a general model blend will be preferred
out through Day 1, and then a blend of the 00Z GFS/UKMET/ECMWF
solutions thereafter through the Day 2/3 period. This will
especially accommodate the spread seen across the southern Plains
and lower MS Valley by the end of the period. The 00Z GEFS mean
still favors the more progressive deterministic GFS, so there
still is some ensemble support for a faster evolution of the
trailing southern stream energy.


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

Orrison