Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
223 AM EDT Tue Oct 02 2018

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 including final preferences and confidence
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...Southeast US into New England...
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Preference: General model blend
Confidence: Above average

06z Update: 00z UKMET/CMC/ECMWF agree well with the 00z GFS/NAM
with the mid/upper level heights and the shortwave tracking across
New England. No major differences noted so a general model blend
is still preferred.

---Previous Discussion---
Subtropical ridging will hold in place across the Southeast US
through the period, bringing seasonably warm temperatures.
Meanwhile, a weak shortwave will trek across northern NY into New
England later today and tonight. Overall, there is fairly tight
clustering within the deterministic model suite for these major
synoptic features with just very minor differences noted in the
strength of the shortwave across New England (00z NAM a bit
stronger). As such, a general model blend including the 00z
GFS/NAM with the 12z ECMWF will be appropriate for this portion of
the CONUS.

...Western US into Northern Plains...
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Preference: 00Z GFS / 00Z ECMWF blend
Confidence: Average

06z Update: Fairly good agreement among all of the 00z guidance
until the end of Day 3 (00z-12z Fri) with the longwave trough
moving into the western US where some timing differences creep up
as the trough axis rounds through southern CA. The GFS was a bit
more amplified compared to the UKMET/CMC and a bit faster compared
to the 00z ECMWF but overall, differences are well within
reasonable spread by day 3.

---Previous Discussion---
Several impulses in the upper level flow will move across the
western US into the northern Plains through the period. A strong
shortwave trough moving into Washington state today will skirt the
northern tier states through tomorrow, spawning a surface low that
will deepen and race into the Hudson Bay area Wednesday night.
There is good agreement between the major deterministic models for
this energy with just subtle timing and strength differences seen
in the low tracks. With the closed low approaching southern CA
then opening up as it moves inland, the 00z NAM/GFS align well its
previous runs and also the other deterministic guidance. It's not
until the end of Day 3 (12z Fri) that more spread is seen in the
models as another shortwave trough approaches the western US. The
00z GFS is a bit slower compared to the 12z ECMWF, while the UKMET
and CMC seem to be somewhat outside the model consensus. There is
also timing and strength differences with northern stream energy
coming into the Pacific NW by 12z Friday.

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

Taylor