Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 315 PM EDT Sat May 30 2020 Valid May 30/1200 UTC thru Jun 03/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Upper level trough and cold front across the Eastern U.S. Saturday-Monday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 00Z Tuesday Confidence: Above average Through 00Z Tuesday - as the upper trough moves east from Great Lakes/Ohio valley through the eastern U.S. - the deterministic model runs and ensemble means are in generally good agreement with the larger scale features. Upper level low slowly lifting from northern Mexico into the southern Plains Saturday-Tuesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average While there are difference with respect to some of its associated smaller scale features, (which fall beyond the scope of this discussion), models are in generally good agreement showing a broad upper low lifting north from northern Mexico into West Texas on Monday, before continuing northeast into northern Texas and Oklahoma on Tuesday. Weakening upper low lifting from Northern California through the Pacific Northwest Saturday and Sunday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 12Z Tuesday, non-UKMET blend 12Z Tuesday-00Z Wednesday Confidence: Average Overall, models are in good agreement showing an upper low currently centered along the Northern California coast transitioning to an open wave as it lifts across Oregon and Washington late Saturday and Sunday. Models remain in good agreement into early Monday as the system continues farther northeast across the Canadian Rockies into central Canada. Significant model differences do not evolve until early Tuesday as system begins to move south of Hudson Bay. As the system begins to round the top of the upper ridge, the UKMET becomes a noted outlier - with a closed system developing south of Hudson Bay. Upper level trough moving from the Pacific Northwest to the northern Plains and Upper Midwest Monday-Tuesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 12Z Monday then, GFS/ECMWF compromise 12Z Monday-00Z Wednesday Confidence: Average With respect to timing, the models are in generally good agreement through early Monday as the system moves east from the eastern Pacific into the Pacific Northwest. However, differences quickly develop as the system moves downstream, with the UKMET, ECMWF and the 00Z EC Ensemble Mean becoming notably faster than the NCEP guidance through the northern Rockies into the Plains and Upper Midwest. While the GFS is still among the slower solutions, it has trended faster compared to its 00Z and previous 12Z solutions. And while still faster than the GFS, the 12Z ECMWF is slower than its 00Z run - suggesting the two models may be moving toward a consensus. Cutoff low developing west of Southern California and northern Baja Monday-Tuesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: UKMET/ECMWF/00Z EC Ensemble mean Confidence: Average Energy dropping southeast across the eastern Pacific is expected to develop a closed low off of the Southern California and northern Baja coasts early next week. Latest guidance shows some differences with respect to the position of the low's center, with the NCEP guidance generally east of the UKMET, ECMWF and the 00Z EC Ensemble Mean. Trends in the GFS support leaning toward the UKMET, ECMWF and 00Z EC Ensemble Mean. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Pereira