Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
101 PM EDT Mon Oct 21 2019

Valid Oct 21/1200 UTC thru Oct 25/0000 UTC

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

12Z Model Evaluation with Preferences and Confidence
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Central U.S. cyclone; secondary low from Carolinas to New England
Tue-Wed.
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Preference: General model blend
Confidence: Slightly above average

The low over the upper MS valley will lift northward into Canada
over the next couple days. Slight strengthening of the low will
continue today, however by tonight the system will become stacked
and fill in as it lifts northward. A secondary low will form over
the Mid Atlantic Tuesday and lift northeastward into New England
through Wednesday. Overall guidance is in good agreement with the
evolution of this system. The 0z ECMWF is probably a tad slow with
the front moving across New England Tuesday night into Wednesday,
otherwise a general model blend should suffice for this system.


Stronger shortwave dropping through Rockies into the southern
Plains early to mid week
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Something close to the 0z ECWMF mean and 12z UKMET
Confidence: Slightly below average

17z Update: The new 12z UKMET did back off a bit from its
deep/slow solution...and is now in between the 0z ECMWF and 12z
GFS solutions (about 2/3 towards the ECMWF). This placement is
probably not a bad place to be at this point...with the 0z ECMWF
ensemble mean a bit weaker/quicker than the deterministic ECMWF
run. Thus at this point would think the most probable outcome is a
bit quicker than the deterministic 0z ECWMF/CMC/UKMET and
something closer to the 0z ECWMF mean and 12z UKMET. Of course we
are still 3 days out so things will change, but for now favoring a
solution near the EC mean and UKMET seems better than going all in
on the slower/deeper deterministic ECMWF/CMC runs. However still
think the 12z NCEP models are likely too weak/progressive.

...original discussion...

Models are in pretty good agreement though 12z Wed (23rd) with the
shortwave energy dropping southward through the Canadian Rockies
and into the northern Plains. Thereafter spread increases
significantly. The non NCEP guidance (ECMWF/UKMET/CMC/EC MEAN) all
show a stronger wave and a trough digging deeper to the southwest
across the Rockies and Plains...eventually resulting in the
development of a cutoff low. The 12z GFS and NAM show a weaker and
more progressive system.

The last several runs of the ECMWF have been very consistent with
the deeper and slower trough...and with the other non NCEP models
trending in this direction as well...it would appear this
slower/deeper solution is becoming increasingly likely. Thus WPC
will continue to prefer a non NCEP model blend for this system
after 12z Wed. Confidence has increased some, but is still
slightly below average given the spread...however if the new 12z
non NCEP models remain consistent with their deeper/slower
solutions, then confidence would increase towards average for this
system.


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

Chenard