Model Diagnostic Discussion
NWS Weather Prediction Center College Park MD
145 AM EST Tue Dec 04 2018

Valid Dec 04/0000 UTC thru Dec 07/1200 UTC

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

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

...Overall Pattern Across the CONUS...
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Preference: Blend of 00Z ECMWF, 00Z GFS, 00Z UKMET
Confidence: Above average

---06Z UPDATE---
No significant change to the preliminary preference. The most
noteworthy model differences continue to be with the trough moving
into the West Coast. However, the 00Z UKMET does appear to have
converged toward the GFS and ECMWF. Therefore, the 00Z UKMET was
included in the preference.

---PREVIOUS DISCUSSION---
From a synoptic perspective, model agreement is excellent through
Wednesday (06/00Z) and still very good through Day 3 / Thursday
Night (07/12Z). In general, the total ensemble spread of height
fields is relatively limited, and this increases confidence in the
forecast overall. Additionally, significant QPF is limited in
spatial extent over the next three days across the CONUS, and thus
most minor model differences do not make a major impact on the
precipitation forecast.

The most noteworthy difference is with the 00Z NAM, which has more
limited precipitation in California despite a similar trough
timing and amplitude to other deterministic models. Given the
strength of the wave and deep southwesterly flow into S/C CA, the
preference is to lean toward the wetter consensus.

The 12Z UKMET and CMC seem to provide a reasonable forecast
overall, and could be incorporated into model blends, but some of
their isoheights aloft are near the outer fringes of ensemble
spread. The UKMET seems to have a slightly more amplified southern
stream pattern and a slightly faster progression than most
ensemble members. The CMC shows greater differences in the
northern stream resulting from greater amplification of several
shortwaves rotating through the Great Lakes. Therefore, the
preference leans toward a blend of the ECMWF and GFS instead.


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

Lamers