Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1133 AM EST Sat Dec 07 2019 Valid Dec 07/1200 UTC thru Dec 11/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS, ECMWF, ECMWF Ensemble Mean Confidence: Average Models are showing some more substantial differences beyond 09.06Z (Sunday Night), particularly with how they handle a southern stream wave digging through the Southwest, and how that eventually phases with a larger, amplifying trough over the Central U.S. This is most notable in a relatively large spread in timing centered around 10.00Z (Monday evening) over the Southwest. Over the past few model cycles, the ECMWF and ECMWF Ensemble Mean have gradually converged around their positions depicted on the 00Z runs. Other models have been less consistent, with the UKMET trending faster and less amplified, and the GFS trending slower. The preference will be to lean toward the 00Z ECMWF and 00Z ECMWF Ensemble Mean, given the multi-run consistency they have shown, and the 00Z GFS given its relatively good alignment with the ECMWF ensemble envelope. Conceptually, the ECMWF also makes sense as the southern stream wave may have a tendency to deamplify and accelerate as it is overwhelmed by larger height falls from the longwave trough expanding over the central U.S. The 00Z CMC and many 00Z NAEFS members hang the southern stream wave back more over the Southwest, and the 12Z GFS has joined that cluster. This can't be completely discounted, but there is a lack of support from other global models. Finally, a preference centered around the 00Z GFS and ECMWF will provide consistency with the previous forecast, as that was the preferred model blend overnight as well. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Lamers