Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1234 AM EDT Wed Oct 02 2019

Valid Oct 02/0000 UTC thru Oct 05/1200 UTC

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

00Z Model Evaluation with Preferences and Forecast Confidence
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...Upper trough crossing the Northern Plains on Day 1....Great
Lakes Day 2, and New England Day 3...
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Preference: Blend of 00z GFS/12z ECMWF
Confidence: Slightly Above Average

The models indicate a closed 500 mb low crosses the northern
Plains to MN by 12z Thu. Clustering among the NAM/GFS/UKMET/Ecmwf
and the respective ensemble means is good.  On Day 2 the system
crosses the Great Lakes while the low opens up into a wave. 
On Day 3, Friday, the wave crosses New England and then into the
coastal waters.  There are minor timing and amplitude differences
with the wave, but spread is less than average.  A multi-model
blend could be used to mitigate the minor differences, for example
blending the GFS and ECMWF.


...Upper trough coming onshore into the Pacific northwest Thu and
crossing the northern Rockies Fri to the northern Plains Fri
night...
Preference: Blend of 00z GFS/12z ECMWF Ensemble Mean/18z GEFS Mean
Confidence: Above Average

The models show a 500 mb trough with a possible embedded closed
low moving across the northeast Pacific to the British Columbia
coast and WA/OR by Thu morning. The trough then crosses the
Pacific Northwest into the Northern Rockies Fri morning.
The 00z Nam starts to get ahead of the pack with slightly faster
timing of the trough. This continues through Day 3/Fri,and is
joined by the 12z UKMET.

The 00z GFS has amplified the trough compared to its older runs,
and is similar in amplitude to the other models, including the
ECMWF. The phasing is slightly different as well, with the 12z
ECMWF and Canadian having a shorter wavelength trough.

The ECMWF and GEFS Ensemble Means are not as sharp/have a longer
wavelength with the 500 mb trough, and are close to the GFS, so a
blend of the ECMWF and GFS Ensemble Means with the 00z GFS should
handle differences.

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

Petersen