Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 136 AM EST Sat Dec 07 2019 Valid Dec 07/0000 UTC thru Dec 10/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00z GFS/12z ECMWF blend Confidence: Average The large closed low off the West Coast will continue to progress eastward and along with stronger amplifying flow out of the northern stream, will evolve into a global scale trof centered from Hudson Bay to Northwest Mexico by Tuesday dominating the CONUS. Initially, the northern stream will inject some shortwave energy into the filling closed low by tomorrow and the northern stream will continue to accelerate and amplify the trof over the Northern Plains; this while the remains of the closed low will descend into the Southwest remaining mildly potent and directing Subtropical Pacific moisture across the the South into the Eastern half of the US in advance of the growing large scale trof. Global guidance has come into much stronger agreement in the placement/timing of the northern stream and southern stream shortwave features through the first few days. This will lead to a large/broad surface trof to develop from SE CO/OK into the Great Lakes by early Monday. As both shortwave features advance, with the Pacific moisture enhanced by return moisture from the Gulf as well as return flow along the Southeast coast; the larger broad cyclone will lift northeast into the Great Lakes deepening and focusing as it tracks along. The ensemble suite has been trending toward a consensus in the evolution of this large system providing some increased confidence. However, the finer/lower scale details still show small variations that lead to shifts/adjustments of the best moisture/forcing axes. As such, this leads to a high confidence preference in the pattern but average to slightly below average confidence in the important sensible weather making details. Still, the operational 12z GFS and 00z ECMWF solution blend appears to be in a typically favorable relation to the ensembles to each other (compared to normal verification)...though the GFS is slightly faster and the ECMWF is slower. The 12z CMC/UKMET, especially in mass fields, are slightly slower but show similar evolution to provide confidence toward a GFS/ECMWF blend even if not preferred in the blend itself. The 00z NAM did trend a bit slower, and is now along the faster fringe of the ensemble clustering, again providing some confidence, like the UKMET/CMC but on the other side of the ensemble cluster. The 00z NAM along with the 12z CMC both continue to have a colder bias in the lower troposphere relative to the other guidance that make it suspect as well, providing another reason to limit both in any blend. While the 12z UKMET is not favored in mass fields, the QPF axis appear to match/provide confidence to the preferred blend (more toward EC), but remains an significant outlier in a wetter solution across AZ/NM; still elsewhere it may help to solidify the QPF magnitude/axis of the preferred blend. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina