Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
236 PM EDT Thu Oct 25 2018

Valid Oct 25/1200 UTC thru Oct 29/0000 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/Eastern US...
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Overall Preference: Blend of 12z ECMWF/GFS/UKMET
Confidence: Average

19z update: The remainder of the 12z guidance (ECMWF/UKMET/CMC)
came in line with the earlier guidance (GFS/NAM) with the
troughing to develop over the eastern US Friday night-Saturday.
While there are some strength differences, the overall tilt and
placement of the trough axis is in pretty good agreement. Some
differences remain for Sunday with the secondary vort max over the
Great Lakes. The ECMWF/UKMET is weaker/more open compared to the
stronger GFS/NAM. For the surface low tracking up the coast, there
is good clustering between the various models...the ECMWF is
slightly more inland compared to the more offshore NAM.

---previous discussion---
Troughing will deepen over the central/eastern US through the
weekend as a surface low tracks up the East Coast. Overall, models
are in reasonably good agreement with the large scale pattern with
the main differences noted across central US with respect to a
couple shortwaves dropping down in the flow.

For the shortwave dropping through Southeast US Saturday, 12z
GFS/NAM are in better agreement with the ECMWF compared to
previous model cycles, while the 00z CMC looks too far south and
strong. As the trough becomes more negatively tilted Sunday, a
secondary vorticity maxima comes through the Upper Midwest, Mid-MS
River Valley. All of the deterministic guidance have similar
placement of this feature but with varying degrees in magnitude.
The NAM and GFS are much stronger compared to the ECMWF, while the
CMC is actually flatter and further north.

At the surface, a low will track up the East Coast Friday into
Saturday. The NAM is faster compared to the consensus and also
deeper. The ECMWF takes the low further inland compared to the
UKMET/CMC/GFS solutions. As far as QPF goes, there are some
magnitude differences between the ECMWF and GFS, though placement
is relatively similar. As such, a blend of the 00z ECMWF/12z GFS
for the central/eastern CONUS is preferred.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
...Pacific Northwest...
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Overall Preference: Non-NAM model blend
Confidence: Slightly above average

19z update: Good consensus with the surface low pushing inland
across B.C. tonight followed by a brief period of ridging/surface
high pressure. A stronger wave then moves onshore Saturday night.
The NAM is too fast with the front coming in compared to the rest
of the guidance, which is reasonably clustered together.

---previous discussion---
A stronger trough will swing through the Pacific Northwest and
B.C. Saturday night into Sunday. There is reasonable agreement
here, though the NAM is faster bringing the trough (and QPF)
inland compared to the ECMWF/GFS. The GFS is stronger (wetter)
compared to the ECMWF while the UKMET is roughly in the middle.
So, a general non-NAM blend is preferred here.


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

Taylor