Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
142 AM EST Mon Nov 12 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 00Z GEFS mean
Confidence: Above average...except for the southern and eastern
U.S. on Day 3 where confidence becomes below 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 from 36
hours onward had tracked the low a bit left of all the other
models, but the 00Z ECMWF has trended farther east and is now very
close to the model consensus which includes the 00Z GFS/UKMET
solutions. The 00Z CMC is close to this camp, but is just a touch
slower with the low track. The 00Z GEFS mean is very close to the
GFS led consensus.

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 00Z CMC is currently the
slowest solution, with the 00Z UKMET now having trended wildly to
being the most progressive. This leaves the 00Z NAM/GFS/ECMWF
solutions in between, but of this group, the NAM is the fastest
and the ECMWF the slowest. In fact, the ECMWF is only a little
faster than the CMC. The 00Z GEFS mean favors a solution that is
in between the ECMWF and GFS.

The overall preference is weighted toward a blend of the 00Z GFS
and 00Z GEFS mean which will best approximate the model consensus
at this point across the CONUS. Confidence in particular across
the southern and eastern U.S. by Wednesday and Thursday is below
average considering the degree of spread among the deterministic
and ensemble guidance. Elsewhere, confidence is actually now
generally above average.

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

Orrison