Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 133 PM EST Mon Jan 07 2019 Valid Jan 07/1200 UTC thru Jan 11/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z ECMWF / 12Z GFS blend Confidence: Slightly above average ...19Z update... Changes in the 12Z ECMWF/UKMET/CMC relative to their previous 00Z cycles were most noted with the 12Z CMC, with the CMC having shifted to the slower consensus with the upper trough axis nearing the West Coast late Thursday. Elsewhere, changes were minimal so no changes to the preference are recommended other than to replace the 00Z ECMWF with the 12Z ECMWF. ...previous discussion follows... The upper level pattern will transition through Tuesday to a general trough-ridge-trough pattern with troughing offshore of the West Coast, ridging in the west-central U.S., and troughing for the northeastern quadrant of the country. Sensible weather impacts will be focused across the West and in the northeastern U.S. through Thursday while the central U.S. stays relatively quiet. One of the areas of the CONUS that has notable model differences is across the Northeast on Tuesday with an amplifying mid-level trough and strengthening surface low near the New England coastline. The 12Z NAM is toward the faster side of the model guidance to pull the closed low/surface low away from New England, with relatively good ensemble agreement and run to run continuity supporting a solution closer to the 00Z ECMWF. The 12Z GFS is a second option here but is displaced farther to the south. The 00Z UKMET/CMC are faster and more to the east with the surface low beyond 00Z/09. Another area with differences is along the California coast on Wednesday with some minor timing differences with a mid-level shortwave in the base of an upper trough/weakening closed low nearing the coast. The 12Z NAM/GFS are faster with this feature whereas the 00Z ECMWF/UKMET/CMC are a bit slower. A 12Z GFS/00Z ECMWF blend is recommended as the ensembles do not show a strong favor to one side or the other regarding timing. The only other system of note is with an upper trough nearing the West Coast late Thursday where the 00Z CMC is much quicker and on the faster edge of the ensemble guidance (near outlier) with this system while the remaining deterministic guidance support a slower timing. Discounting the faster 00Z CMC, the impacts of this system remain well offshore through 00Z/11. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto