Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 123 PM EDT Thu Jun 04 2020 Valid Jun 04/1200 UTC thru Jun 08/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Confidence ...Wavy front with low pressure crossing the Great Lakes towards northern New England this weekend... Preference: Blend of 00z ECMWF/12z NAM/12z GFS Confidence: Average The models show similarly to one another concerning the timing of a front crossing the Great Lakes Fri and the northeast Saturday. Waves of low pressure may develop along the front and the 00z-12z UKMET were outliers with the low pressure several mb stronger than other solutions, which changes the frontal timing. Given good clustering among the 00z ECMWF/12z NAM/12z GFS and their respective ensemble means, a blend of these operational runs is preferred. ...Initial cut-off low offshore southern California, moving onshore Friday and into Great Basin Saturday and Montana Saturday night... Preference: Blend of the 00Z ECMWF/12Z GFS/12z UKMET Confidence: Slightly above average A cut off upper low will move slowly northeast Friday and move onshore into southern California Friday evening. The low opens up as it moves inland within confluent flow and becomes an open wave and deamplifies as it moves north across the Great Basin Saturday. The shortwave energy merges with the northern stream closed low over the Pacific northwest, with the models showing a 700-500 mb wave and sfc flow developing in MT Saturday, with the sfc low crossing into Canada by 12z Sun in most guidance. Even the low developing in ID and moving into MT Sat has good clustering among the 12z NAM/12z GFS/00z ECMWF/00z-12z UKMET. The good clustering supports a model blend to mitigate minor timing and location differences. ...Closed low off British Columbia drifting south through Friday night and then off Washington/Oregon Saturday, moving east and onshore Saturday night-Sunday... Preference: 12Z GFS/00z ECMWF/12z UKMET blend Confidence: Slightly above average The 12z NAM/GFS/12z UKMET/00z ECMWF cluster well with the closed 500 mb low moving south offshore from British Columbia Friday, then off WA/OR Saturday, then moving the low onshore Saturday night, and into the Northern Rockies Sunday. There is better than usual clustering among these models and their respective ensemble means. The 00z Canadian was the slow outlier, lagging west of the primary cluster by several hours. Therefore, the preference is toward a blend of the 12Z GFS/00z ECMWF/12z UKMET. Only very minor changes were noted with the 00Z ECMWF/12z UKMET/GFS compared to their prior cycles. ...Tropical Cyclone Cristobal... Preference: 15Z NHC advisory Confidence: Refer to NHC products The 00Z ECMWF is close to the official track for T.S. Cristobal through Day 2. The 00z Canadian and 12z GFS were slightly faster on Day 2 but slow down on Day 3, to merge more closely with the ECMWF track. The 12z UKMET, previously on the eastern edge of the guidance suite, has trended west towards the ECMWF/NAM/GFS/Canadian global. The 12z NAM takes a sharp left turn 72-84 hours, bringing out of alignment with other model solutions and the official NHC track. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Petersen