Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1144 AM EST Sun Nov 04 2018 Valid Nov 04/1200 UTC thru Nov 08/0000 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: 00z ECMWF and 12z GFS in eastern half of North America 00z UKMET/ECMWF and 12z NAM in Northwest/Canadian Rockies after 06/12z Confidence: Slightly Above Average in eastern half of North America Slightly below average in Northwest/Canadian Rockies after 06/12z. Models try to consolidate on a common solution and appeared to have done so with the lead wave lifting across the Midwest currently as well as the general timing/spacing with the approaching strong jet and shortwave along its nose currently in the Intermountain West. Generally, there is growing consensus to the shape but given the system takes a broad (global trof) yet still negative tilt with the internal smaller scale lead shortwave through MO/AR on early Tuesday developing a strong surface low that rolls quickly from S IL into the Great Lakes with significant deepening. Small differences in timing and magnitude of latent heat/upscale feedback from the convective development lead to slight longitudinal differences in the sfc low track...with fast/strong solutions like the 00z UKMET being west and flatter solutions like the 12z GFS furthest east. The 00z ECMWF is most central and consistent within the global suite just a bit west of the GFS; the 00z CMC is a clear outlier and like the 12z NAM favors a stronger shortwave along the US/Canadian border closer to the deeper cold air source. The NAM has been similar to the CMC but the 12z run while still strong aloft, is starting to intersect lower level moisture flux/convergence further east toward the ECMWF axis. All in all, WPC will favor the ECMWF solution, followed by the GFS and some NAM at times (not across the Northern Plains with the deeper center shortwave as it slides eastward by Wed). Confidence continues to grow with this growing consensus but given small timing difference lead to mild to moderate spread, confidence cannot be above average. In the wake of the main shortwave/jet streak, there is large model spread with the trailing/entrance region of the jet as well as the mean trajectory of the deep Arctic cold pool that slowly marches south out of Northern Canada. The 12z GFS, like many prior runs is quite quick, leading to a flatter solution and a NW to WNW trajectory of the cold air toward the Central Canadian Providences, supported by the NAM and CMC. The 00z ECMWF is very cold and compact with the wave descending out of Western Canada (east of the Rockies), dominating the Pacific stream of energy in the mass fields, and strong confluence across WA/ID/MT by 00z Thursday the 8th, the UKMET supports the ECMWF generally, but not to the magnitude. Given downstream influences and typical biases, it is likely clear that neither solution will ultimately evolve in reality but would favor something closer to the ECMWF, so a preference of the UKMET and ECMWF is favored but injected with the NAM a bit to hedge a bit more middle ground. Obviously, confidence is not very high (slightly below average for this region after 06/12z). Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina