Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1229 PM EST Thu Nov 22 2018 Valid Nov 22/1200 UTC thru Nov 26/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 12Z NAM, 00Z ECMWF, 00Z CMC, 06Z GEFS Greatest weight to 00Z ECMWF Confidence: Slightly Below Average There is general model agreement on the sequences of significant waves that will be propagating across the CONUS in the next few days. However, there are some important differences that will impact precipitation patterns and sensible weather. Normalized standard deviation of 500mb heights from the 00Z ECMWF Ensemble is greater than 1 over a significant portion of the CONUS indicating greater ensemble spread than we've seen over the past 30 days. One area of notable disagreement is with the amplitude of a negatively tilted shortwave that will be lifting out of the Northeast later this weekend. The 00Z ECMWF shows considerably more amplitude with this wave than the other models, while the 12Z GFS seems more progressive than model consensus. The preference in this specific area is to lean toward a general blend of available models, but to place less weight on the ECMWF and GFS. Another area of notable disagreement is with a digging wave that will be emerging into the Plains on Sunday and lead to a deepening low in the Midwest. Ensemble sensitivity analysis shows that a considerable amount of the variance can be traced back to the amplitude and strength of the associated wave as it reaches the Pacific Northwest coast in a couple days. A weaker wave would lead to a weaker low and a flatter, faster low track downstream over the Midwest, while a stronger wave would lead to a stronger surface low further to the northwest. The 12Z GFS and 00Z UKMET show a faster surface low, while the 00Z ECMWF, 00Z CMC and 12Z NAM are slower and stronger. The preference is to lean toward the ECMWF, CMC and NAM, which are supported by a greater number of 06Z GEFS members and 00Z ECMWF Ensemble members. The GFS and UKMET fail to close off a mid-level low, which seems less likely given a strong, digging wave that is likely to be associated with strong cyclogenesis and an increasing negative tilt to the wave with time. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Lamers