Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1234 PM EDT Sat Oct 27 2018

Valid Oct 27/1200 UTC thru Oct 31/0000 UTC

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

12Z Model Evaluation...with Preferences and Confidence
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...Overall Pattern Across the CONUS...
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Preference: Blend of 12z GFS/NAM, 00z UKMET/ECMWF (non-CMC blend)
Confidence: Slightly above average

Through early next week, the synoptic pattern across the CONUS is
expected to shift from deep troughing over the eastern US toward
the central Plains / Rockies. A couple of shortwave troughs will
push through the flow across the northern US. By the middle of
next week, surface high pressure transition toward the southeast
US while an area of low pressure develops across the lower MS, TN,
and OH River Valleys. This will set up an active pattern with
several rounds of rainfall.

In general, the deterministic model guidance is in good agreement
through early next week, replacing the troughing over the eastern
US with more zonal flow. Energy from the western US will
eventually move toward the Rockies and Central Plains, carving a
trough. The NAM/GFS/ECMWF are in reasonable agreement here with
the vorticity maxima while the UKMET is similar in placement but
stronger in magnitude. With Gulf moisture opening up and advecting
toward the mid-MS to lower Great Lakes, the QPF fields are in good
agreement. The GFS trended toward the 00z ECMWF, though is still a
bit faster. The CMC is considerably faster than the rest, while
the UKMET is a decent compromise between the GFS/ECMWF. The NAM's
QPF is overall lighter than the rest, but the placement agrees
well with the GFS/ECMWF/UKMET. Another area of low pressure will
push into the Pacific Northwest Tuesday into Wednesday, bringing a
spell of wet weather. Here, the 00z ECMWF was faster than the the
rest of the models.

So, outside of the Northwest US, a blend of the
GFS/UKMET/NAM/ECMWF (basically non-CMC) is preferred. While for
the Pacific Northwest, a similar blend can be used but with less
weight toward the ECWMF.


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

Taylor