Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1157 PM EST Sun Nov 11 2018

Valid Nov 12/0000 UTC thru Nov 15/1200 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: Blend of the 00Z GFS and 18Z GEFS mean
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. with two amplifying shortwaves
diving south through the Intermountain West. Over the next 1-2
days, the mean layer troughing over the central U.S. will shift
east with two components, a northern stream and a southern
stream...with the southern stream getting left behind over the
south-central U.S. Tuesday into Wednesday. Across the West, the
northern end of the ridge axis will be eroded by a shortwave
trough Tuesday and Wednesday associated with a cold front at the
surface reaching the Pacific Northwest.

At the surface, a low will hug the western and central Gulf Coast
tonight through Monday night at which point cyclogenesis will take
place along the northern Mid-Atlantic coast. The surface low will
deepen while tracking along the New England coast on Tuesday,
quickly exiting into the Canadian Maritimes by Wednesday morning.
There is some spread among the models regarding the details of the
low track, as the 00Z NAM is a touch faster than the global models
from 30 to 48 hours, and then comes into better alignment with the
model consensus beyond this time frame. The 12Z ECMWF though from
36 hours onward tracks the low a bit left of all the other models
while the 12Z CMC tends to be a bit farther east. The 12Z UKMET
and 00Z GFS are in between camps, with the GFS in particular
having better ensemble support from the GEFS mean and even to some
extent the ECENS mean.

Trends over the last 24 to 36 hours have definitely favored more
separation between the northern and southern stream components of
the longwave trough over the central U.S. All of the models are
favoring southern stream closed low development over the southern
Plains by Tuesday as strong northern stream troughing advances
across the Great Lakes and Northeast. The 12Z UKMET/CMC solutions
are by far the slowest with the ejection of the closed low
feature. The 00Z NAM is now suddenly the most progressive with the
00Z GFS a bit slower, but faster than all of the non-NCEP models.
The 12Z ECMWF is faster than the UKMET/CMC solutions, but a bit
slower than the GFS. The NAM and GFS are showing notably more
progressive trends and are faster than all of the ensemble means
at this point.

The overall preference is weighted toward a blend of the 00Z GFS
and 18Z GEFS mean which will accommodate concerns that the ECMWF
is a tad too far left with the low track along the East Coast with
the initial system, and that the ECMWF and the remaining non-NCEP
models are too slow with the southern stream closed low going
through Wednesday and Thursday. This blend will also suffice with
the shortwave energy crossing into the Pacific Northwest where
model spread here is actually rather minimal.

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

Orrison