Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 224 AM EDT Sun Jul 26 2020 Valid Jul 26/0000 UTC thru Jul 29/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-upper level troughing over the northern CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Mid to upper level energy over southern Canada is expected to close off before settling over Ontario later in the period, while the larger scale trough deepens over the Great Lakes region. At the surface, a pronounced cold front is forecast to march across the northern tier into the Great Lakes while upstream ridging builds over the Canadian Rockies. In the increasingly amplified pattern, the models have converged on a similar idea and show very good agreement through 84 hours with the synoptic pattern. ...Tropical Storm Hanna... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Official NHC track Best Model Proxy: Non-GFS model blend Confidence: See latest NHC products Gradual weakening over land will occur as the system tracks westward then southwestward into the rugged terrain of Mexico on Sunday and Sunday evening. The biggest spread in the models occurs after the system moves into Mexico where the GFS is on the southern side of the model spread. A CMC/ECMWF/UKMET/NAM blend is the best proxy to the official forecast and for the latest information on Hanna, please consult the latest NHC public advisory. ...New upper trough/low approaching California by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend Confidence: Slightly Above Average Toward the end of day 2 and into day 3, another shortwave trough approaches the Northwest Pacific and northern CA in all of the guidance except the 00z UKMET which keeps the southern stream shortwave in place west of 130W longitude. The 00Z guidance is otherwise in good agreement showing some slight depth issues with the northern stream shortwave moving by the Pacific Northwest late Tuesday. As an approaching upper level low should act as a kicker for the shortwaves in both streams Tuesday night, believe the 00z UKMET has no support from the synoptic pattern either. A compromise of the 00z GFS, 00z Canadian, 00z NAM, and 00z ECMWF is preferred with slightly above average guidance. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml This product will terminate August 15, 2020: www.weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination. pdf Roth/Taylor