Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
314 PM EDT Mon Oct 28 2019

Valid Oct 28/1200 UTC thru Nov 01/0000 UTC

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

12Z Model Evaluation with Preferences and Confidence
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...Mid-level trough ejecting into the central Plains...
...Shortwave/clipper low over MT/ND this evening...
...Surface cold front over the lower/mid MS Valley by Tuesday...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Above average

Shortwave energy currently over the central Rockies will eject out
into the central Plains and advance northeastward toward the Upper
Midwest the next 24 hours. There is above average model agreement
and continuity such that a general model blend will suffice.


...Powerful closed low over the Intermountain West by Tuesday...
...Energy advancing east across the Plains Wednesday...
...Cold front/surface wave near OH/TN Valleys by Thursday...
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Preference: Blend of the ECMWF/ECENS mean
Confidence: Average to slightly below average

19Z update: No significant changes noted with the rest of the 12Z
guidance now available. The GFS remains a faster outlier with the
trough axis on Day 2/3 and the NAM is considerably slower on Day
3. The ECMWF and to some degree the UKMET/CMC offer a compromise
solution. At the surface, the CMC takes the low well northeast
(north of Maine) while the rest of the guidance seems to be
clustering on an eastern Great Lakes position by 01.00Z. With this
in mind, the preference will remain the same for a ECMWF/ECENS
mean blend, especially Day 2/3 when confidence is below average.

---previous discussion---
With strong ridging aloft across the eastern Pacific, shortwave
energy dropping south into the northern/central Rockies Tuesday
will dig vigorously and eventually close off across Colorado.
Through 48 hours, model agreement is average except for the latest
GFS, which continues to be too fast/progressive with the overall
evolution of the system. Its differences are less than previous
runs but still significant enough to be excluded from the forecast
preference at this time.

The system then slowly ejects into the central Plains through
Thursday with the GFS remaining ahead of the rest of the
deterministic guidance and ensemble means. Several waves of low
pressure are forecast to develop and move through the TN/OH
Valleys late week eventually consolidating into a deeper system
over the Great Lakes by the end of the week. The NAM becomes too
slow by Day 3 and is not as usable then. There is fairly good
agreement with the latest ECMWF and ECENS mean and perhaps even
some utility in the GEFS mean as well. Confidence becomes degraded
though by the end of the period given the overall deterministic
model spread.


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

Taylor