Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 228 AM EDT Fri Aug 03 2018 Valid Aug 03/0000 UTC thru Aug 06/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation Including Preference and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Synoptic Pattern across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend exclude 00z GFS in the northeast Confidence: Slightly above average 07z update: The 00z UKMET/ECMWF trended a bit faster/deeper with the initial wave emerging from the central Rockies into MN/SW Ontario, precursory to the positive tilt trof in Canada. This brings better overall alignment through away from the ensemble means and closer to the 00z NAM (though still much less amplified). This would suggest a Non-NAM blend remains preferred through the domain...especially with essentially no significant departure in the Northeast for the UKMET/CMC and ECMWF. So a Non-NAM blend throughout the domain, with exclusion of the 00z GFS in the Northeast is final preference. ---Prior Discussion--- Deep latitude trof over the east is breaking down quickly in the short term but the trailing wave currently in GA will phase with compact shortwave rounding the southeast side of the subtropical ridge as both lift into the Northeast by Sat. The 00z GFS continues to be quick with reduced phasing, while the ECMWF, CMC, and UKMET show greatest agreement in the center of the ensemble suite (GEFS/CMCE and ECENS), While the 00z GFS is fast, it at least showed a similar track/placement while tracking up the coast; this is opposed to a more amplified/wound up NAM solution that was well north of the ensemble means. As such would favor away from the NAM/GFS in the Northeast. Into the southeast Gulf of AK, a very strong/vast closed/stacked low is fairly well agreed upon with only very small timing differences within the inner core of the upper low itself, enough to support a general model blend at above average confidence here. It is between this deep low and the weakening deep latitude wave over the East, that highly variable, weak shortwave features provide larger scale zonal flow, but more synoptic waviness that eventually amplifies into a larger broad trof across central Canada into the Northern Tier of the US by Sunday into Monday. A lead wave currently in the central Rockies, rounding the top of the Southwest ridge, will amplify as it slides northeastward into Ontario...here the NAM is clearly over amplified, though the 12z CMC looks a bit slower but deeper as well. The CMC is not terrible out of phase with the 00z GFS and 12z UKMET/ECMWF and the ensemble suite, but may be best to weight lower for this combination of smaller scale waves as that grow upscale by Monday. Confidence is a bit reduced for this feature but only slightly so. All in all, a Non-NAM blend is supported across much of the CONUS but reduce the CMC in the north central US (Canada) and eliminate the 00z GFS in the northeast for greatest forecast confidence (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