Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 246 AM EDT Wed Aug 08 2018 Valid Aug 08/0000 UTC thru Aug 11/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation and Preferences with Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Synoptic Pattern across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: NW CONUS: Non-CMC blend Central/Eastern CONUS: Non-NAM blend Confidence: Slightly above average 07z update: The greatest model variance is related to the timing of the closed low approaching the Pacific Northwest. The 00z UKMET shifted faster falling in line with the prior preference, 00z NAM. The 00z CMC took the 12z UKMET's place significantly slowing due to more compact/concentric solution. The 00z ECMWF also slowed, merging/phasing with northern stream energy at landfall. It is not too out of phase, and would support shifting toward Non-CMC in this area. Elsewhere the 00z UKMET trended much better to agree with the timing/shape and placement of the main shortwave features and frontal/convergence zone through the south/Carolinas. Enough to strongly support its inclusion in the mass field blend with the 00z ECMWF/GFS/CMC across the remainder of the Central/Eastern CONUS. ---Prior Discussion--- Overall synoptic to global pattern is well agreed upon with closed low/amplified ridge/and broad eastern half of the CONUS in the trof, which is seen well in the last 4 cycles/ensemble trends. However, mesoscale to synoptic details show subtle but important differences, typical of each model bias, and particularly into day 3. The exiting mean Canadian trof that stretches into the northeast, with associated surface wave in Northeast (Thursday) is fairly well timed, but models either show greater stretching or greater concentric solutions with the base of the trof through the Northeast. The 00z NAM is most concentric and therefore slower exiting by Friday to not desire its inclusion in any blend here. Similarly, the lingering positive tilt trof that starts to consolidate/amplify across the Lower MS valley Friday is most aggressively compact by the 00z NAM and ejects further/faster toward the east. While, the 00z GFS/ECWMF are a bit more elongated/stretched through into the Red River Valley matching well with the overall ensemble trend and likely evolution given the breadth of diffluent flow across the Midwest/MS valley, hinting on some weak retrograding across TX into northern Old Mexico. The 00z GFS does shear the wave toward the east eventually a bit faster than the ECMWF, but not significantly so, to blend the two. The 12z UKMET shows greater similarity to the less favorable NAM. Further west, the closed low off the west coast will reach the Pacific Northwest in the Friday/Saturday time frame. Here the 12z UKMET is very slow and well out of phase with the remaining guidance. The 00z GFS slightly outpaces the means, per typical bias but not significantly so, but would favor something closer to the ECMWF/CMC/NAM. Overall, a blend of the 12z ECMWF/00z GFS and lower weighting/inclusion of the 12z CMC seems an appropriate blend given trends/continuity and overall confidence. Confidence remains slightly above average. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina