Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
1141 PM EST Mon Nov 12 2018
Valid Nov 13/0000 UTC thru Nov 16/1200 UTC
...See NOUS42 KWNO (ADMNFD) for the status of the upper air
00Z Model Evaluation...with Preferences and Confidence
...Overall Pattern Across the CONUS...
Preference: Blend of the 00Z NAM/GFS and 12Z ECMWF
The synoptic pattern currently features an upper level ridge over
the western US with downstream troughing across the central US. A
couple of shortwave troughs are embedded in the flow, with one
digging across the northern tier of the U.S. and southern Canada
while another is amplifying down across the southern High Plains.
Over the next 24 to 36 hours, the southern stream shortwave will
slow and become further detached/removed from the northern stream
energy/flow and evolve into a closed low over north Texas, which
is where model uncertainty begins to increase. The 12Z UKMET is
considered an outlier, as it is considerably faster than the rest
of the global deterministic models with the progression of the
closed low downstream across the lower MS/TN Valleys and toward
the central Appalachians and Mid-Atlantic region through Thursday
and Friday. The 00Z NAM/12Z CMC and 12Z ECMWF are all clustered
toward the slow side of the model spread with the 00Z GFS in
between camps. The mass fields of the CMC though become more out
of tolerance by Friday as it opens up the closed low into a
progressive trough versus the NAM/GFS and ECMWF which all take a
closed low from the TN Valley east across the Mid-Atlantic region.
By comparison, there is better model agreement with the track and
strength of the surface low that forms near the Southeast
coastline and lifts northeast up along the East Coast Thursday and
Friday. The NAM is likely a bit too weak with its low, but the
UKMET appears too strong and too progressive. The latest ensemble
means are generally split with the details of the upper
trough/closed low evolution, with the GEFS favoring the GFS and
the ECENS favoring the ECMWF.
Meanwhile, the models all support the deep layer ridge over the
West breaking down a bit and allowing a northern stream shortwave
to drop down near the Pacific Northwest and through the northern
Plains going Thursday and Friday which will allow a surface low
and cold front to advance southeast over the northern High Plains.
The UKMET appears too far north with its surface low with this
energy and the CMC too weak. Better clustering resides with the
NAM/GFS and ECMWF.
Based on the latest model clustering and trends across the CONUS,
the overall preference is weighted toward a blend of the 00Z
NAM/GFS and 12Z ECMWF.
Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml
500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml