Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
235 PM EDT Mon Oct 14 2019

Valid Oct 14/1200 UTC thru Oct 18/0000 UTC

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

12Z Final Model Evaluation with latest Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


Closed mid level low and surface lows affecting the Great Lakes
and Northeast Tue into Thu
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non 12z GFS blend
Confidence: Average

The 12z NAM is close to the model consensus with the closing mid
level low over the Upper Great Lakes Tue. It remains close to the
consensus as it takes on a negative tilt across northern New
England late Wed into Thu. While it is close to the model
consensus with the primary surface low over southwest Quebec Wed
afternoon/evening, it develops a secondary surface low off the
Southeast coast much earlier than the remainder of the guidance,
tracking it into ME by 18/00z.

The 12z GFS (as well as the 12z GEFS mean), however, is faster
than the consensus throughout the process, with the secondary
surface low tracking through northern New England much faster than
the consensus. Because of this, the 12z GFS is not included in the
preferred blend, as the 12z non-NCEP guidance is closer to the 12z
NAM with the evolution of the secondary surface low.


Short wave energy affecting Texas Wed/Thu
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Average

Short wave energy at the base of the developing long wave trough
off the West Coast early Wed tracks across the Southwest states,
reaching central TX by 18/00z. There is some spread with this
system as it reaches TX, with the 12z GFS/12z GEFS mean a bit
faster than the 12z ECMWF/00z ECMWF ensemble mean. However, the
spread is not so great as to eliminate any ensemble or
deterministic solution at this time. Therefore, a general model
blend is preferred, but because of the spread, forecast confidence
with respect to the placement is just average.


Developing long wave over the West Coast Wed/Thu
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: General model blend
Confidence: Average

Both the 12z NAM/GFS are in line with the model consensus
concerning how the strong closed low south of the Gulf of Alaska
drops to just west of Vancouver Island before 17/00z. Short wave
energy diving south from the closed low aids in carving out a long
wave trough near the West Coast by 17/12z, which tracks into the
Northern Rockies and Southwest by the end of the period. The 12z
UKMET/CMC/ECMWF are close to their previous solutions, maintaining
the model consensus.

While there are some minor timing differences with respect to how
quickly the long wave trough develops, there is enough model
agreement to support a general model blend for Wed into Thu.


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

Hayes