Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
326 AM EDT Thu Sep 20 2018

Valid Sep 20/0000 UTC thru Sep 23/1200 UTC

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

00Z Model Evaluation...with Latest Preferences and Confidence
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

...Overall preference for the entire CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Non-CMC blend, less weight on 00Z GFS
Confidence: Slightly above average

---07Z UPDATE---
No significant change to the preliminary preference with the
remainder of the 00Z model cycle. Removed the CMC from the
preference, as the 00Z CMC shows notable differences with the
trough over the Southern Plains (far less amplified) and the
timing and amplitude of the trough pushing into the West Coast
this weekend.

---PREVIOUS DISCUSSION---
Models show fairly good agreement overall across the CONUS over
the next several days, with the greatest difference (and impact on
QPF) in the weaker flow over the southern US. The 00Z GFS shows a
greater retreat of the ridge of high pressure extending from
Bermuda into the Carolinas by this weekend, which allows the
southern stream trough and associated sheared lobe of vorticity to
make faster progress to the east. The GFS and its associated
ensemble members (12Z and 18Z runs) were generally faster with
this progression than most of the other deterministic models and
ECMWF ensemble members. Given the greater consistency with the
non-GFS models, the preference is to place more weight on those
models. However, the GFS is similar enough with its mass fields
overall that it is included in the preference.

Outside of the south-central US into the Ohio Valley, model
differences had minimal impacts on QPF.


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

Lamers