Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
204 PM EST Tue Nov 13 2018

Valid Nov 13/1200 UTC thru Nov 17/0000 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 the 12Z NAM/GFS/ECMWF
Confidence: Average

19z update: The ECMWF continues to be a bit slower with the upper
level low progression across the lower Ohio Valley into the
mid-Atlantic, compared to the GFS. But the spread between the two
is considerably lower compared to 24 hours ago. The ECMWF surface
low track up the eastern coast is just left/west of the GFS but
again, fairly similar. In general, model spread is lower as
forecast confidence has improved.

---previous discussion---
An upper level shortwave currently over the southern Plains will
become closed in the next 24 hours as it drifts east/northeast
toward the mid-MS and lower Ohio Valleys. At the surface, a low
pressure will develop along a stalled frontal boundary and deepen
as it moves up the East Coast. This will bring an early season
wintry event to portions of the mid-MS, lower Ohio Valley as well
as portions of mid-Atlantic and Northeast.

In the upper levels, the models are in good agreement with the
track and strength of the closed in the first 48 hours, then as it
opens up and becomes negatively titled off the mid-Atlantic and
Northeast US.

At the surface, there continues to be differences in the later
forecast period with the low track. The 12z NAM is more inland
compared to the 12z GFS and 00z ECMWF (which are well clustered),
and then becomes too fast compared to the rest of the model
guidance.

Meanwhile, the models all support the deep layer ridge over the
West breaking down a bit and allowing a pair of northern stream
shortwaves to drop down near the Pacific Northwest and through the
northern Plains and upper Midwest going through Thursday and
Friday. The first shortwave will drive a surface low across
southern Canada along with a cold front, with the second shortwave
dropping a little farther south down across the northern High
Plains which will allow a new surface low and the same the same
cold front to drop across this region. The NAM has its ridge axis
further to the west, allowing the northern stream energy to push
more across coastal areas compared to the GFS/ECMWF/UKMET.

Based on the latest model clustering and trends across the CONUS,
the overall preference is weighted toward a blend of the 12z
GFS/NAM and 00z ECMWF.


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

Taylor