Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
257 PM EDT Thu Oct 10 2019

Valid Oct 10/1200 UTC thru Oct 14/0000 UTC

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

12Z Model Evaluation with latest Preferences and Confidence
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...Deep closed low near the 40N/70W benchmark...
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Preference: General model blend...through 48 hours
            12Z ECMWF...after 48 hours
Confidence: Slightly above average

A deep area of low pressure situated just southeast of the 40N/70W
benchmark has generally leveled off in intensity and is forecast
to make a slow counter-clockwise loop over the next couple of days
before tracking out to sea. This storm is currently blocked by a
large low to mid-level high over eastern Canada and part of a Rex
block pattern. The latest ECMWF and CMC have trended toward the
timing cluster of the NAM/GFS and UKMET with respect to the timing
of the cyclonic loop that takes place. As the storm system pulls
away and weakens by Saturday, there is some latitudinal spread
among the guidance with the low track, as the NAM and UKMET take
the system north of the GFS and CMC. The new ECMWF splits the
difference between camps. A general model blend will be preferred
at this point through 48 hours, followed by a solution toward the
ECMWF as a compromise thereafter.


...Deep Plains/Upper Midwest Cyclone...
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Preference: Blend of the 12Z GFS/UKMET/CMC
Confidence: Above average

A strong deep layer trough and associated closed low over the
northern Rockies will be advancing east this afternoon across the
High Plains and will continue to deepen tonight through Friday as
the system pivots across the upper Midwest. The models are in good
agreement overall, but the latest ECMWF still tends to
cyclonically pivot its low center a tad farther back to the
northwest across areas of northwest MN versus the NAM/GFS/CMC and
UKMET. The ensemble means are split on this as the 00Z ECENS mean
supports the ECMWF, and the 12Z GEFS mean supports the
NAM/GFS/CMC/UKMET cluster. The NAM is also seen as being perhaps a
bit too strong/deep with its mid-level low center. Meanwhile, a
very strong cold front will advance quickly east across the
lower/mid-MS Valley and OH/TN Valleys by late Friday, before then
reaching the East Coast on Saturday. The UKMET is perhaps a tad
slow with the cold front, but overall there is good timing
agreement among the models with the front. Regarding the deep
closed low over the upper Midwest, a pronounced weakening trend is
expected on Saturday as the system becomes vertically stacked. All
of the models show good agreement on the weakening trend at this
point, and take the system gradually across the upper Great Lakes
and into Ontario through Sunday. The ECMWF and ECENS mean are
periodically a bit more out of phase with the other models with
its placement of the surface low, but otherwise the guidance
reflects fairly good clustering. The preference at this point will
be toward a blend of the GFS, CMC and UKMET given concerns about
the ECMWF low placement and at times, and with the NAM probably
being too strong in the mid-levels with the closed low.


...Western U.S....
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Preference: Non-CMC blend
Confidence: Above average

A progressive shortwave trough will advance inland from the
Pacific Ocean on Sunday and advance into the Great Basin. The
models show good timing and depth agreement, but the CMC appears
to be somewhat of a progressive outlier by the end of the period.
The remaining deterministic guidance and ensemble means favor
going with a non-CMC blend, and that will be the preference.


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

Orrison