Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1147 PM EST Sun Feb 10 2019 Valid Feb 11/0000 UTC thru Feb 14/1200 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 12Z ECMWF, ECMWF ENS, UKMET Confidence: Average, except Slightly Below Average along the West Coast A retracting North Pacific jet will lead to a complex split flow regime downstream over the Northeast Pacific Ocean over the next few days. As a result, the greatest source of model spread is with the trough that will be digging down the West Coast on Tuesday and Wednesday. Otherwise, model spread is fairly typical with a wave ejecting into the Plains and becoming negatively tilted with strong cyclogenesis northeastward into the Great Lakes by Tuesday Night. Thus, the model preference is not strongly tailored toward one specific model to the east of the Rockies. A general model blend should adequately capture the forecast uncertainty and provide a reasonable consensus forecast. However, one exception would be with the 12Z CMC, which is slower and more amplified with the wave aloft than essentially all available deterministic models and ensemble members (including from the CMC ensemble), and evolves the low-level cyclone in a different way entirely (with secondary cyclogenesis over the interior Northeast rather than along the coast as depicted by the other models). Along the West Coast, there are substantial differences with respect to the amplitude of the digging trough, as well as lesser (but still noteworthy) timing differences. This seems to primarily result from variability in how the digging wave interacts with low-amplitude waves arriving from the central Pacific. The 12Z ECMWF and UKMET (and many of the ECMWF ensemble members) show more phasing of the waves, resulting in a broader trough that digs further southeast. The 00Z GFS and NAM are less amplified and show less phasing, with the strongest height falls concentrated further north. The 12Z CMC offers a trough position that is more advanced and amplified than many ensemble members, and thus is not preferred. However, CMC ensemble members do show more overlap with ECMWF ensemble members, and this supports a preference that leans toward the ECMWF and UKMET. Despite much of the precipitation maxima being terrain-driven, this does has implications for both southward extent of heavy precip (ECMWF/UKMET bring it further south) and placement of precipitation on some of the interior ranges. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Lamers