Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 123 PM EDT Wed Jun 03 2020 Valid Jun 03/1200 UTC thru Jun 07/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation Including Final Preferences and Confidence ...Frontal wave moving from the mid MS Valley Fri across the midwest and Great Lakes to Ontario Friday and northern New England Sat... Preference: Blend of 00z ECMWF/12z GFS Confidence: Normal The models indicate a front boundary moving slowly east from the central Plains and upper MS Valley with low pressure developing along the front in the midwest and then moving across the Great lakes into Ontario. The 00-12z UKMET have both developed stronger low pressure but the 12z Fri positions were off by about 180 nm (12z run further east in IL with low pressure location). With the deeper low and lack of run to run continuity, confidence is low in either the 00-12z runs of the UKMET. Given better agreement among the GFS/00z ECMWF/ECMWF Ensemble mean, I recommend blending the better clustered solutions. Cut-off low moving from offshore southern California moving onshore Friday and into Great Basin Saturday Preference: Blend of the 00z ECMWF/12z UKMET/12z GFS Confidence: Slightly above normal A cut off upper low will move slowly northeast Friday and move onshore into southern California Friday. The system opens up as it moves inland in confluent flow, with slight timing differences. Given the 12z UKMET timing was close to the 00z ECMWF and the EC mean, so good clustering of solutions lends itself to a consensus-based approach. ...Closed low drifting south off British Columbia through Friday night and then off Washington/Oregon Saturday, wave moving into northern high Plains Saturday... Preference: Blend of 12z UKMET/00z ECMWF/12z GFS Confidence: Slightly above normal An upper level low is expected to drop south, west of the British Columbia coast, and be situated west of the Washington coast by Saturday morning. The low may approach the Pacific northwest coast Sat night. The 12z NAM was a bit deeper than the other models, with good agreement among the 12z UKMET/12z GFS/00z ECMWF. At 700 mb, the models show a wavy warm front crossing the northern Rockies Saturday and then onto the northern Plains. The 12z NAM had stronger low pressure near the SD/NE border than other models, and the CMC global had different timing/phasing at 500 mb. The good agreement among the 00z ECMWF/12z UKMET/12z GFS supports a consensus of those 3 models. ...Upper trough drifting east across the lower MS Valley and southeast... Preference: General model blend Confidence: Slightly above normal A broad upper trough will track eastward across the lower MS Valley Thursday, and into the southeast Friday and Saturday, with an upper ridge building east from the central Plains to the mid MS Valley Sat. The 500 mb trough axis will extend southward over the northern Gulf of Mexico, and this will be important since upper level flow ahead of it will play a role in the future track of Tropical Storm Cristobal. The 00z ECMWF and 12z GFS are in close enough agreement on the main features to merit the use of a blend. ...Tropical cyclone Cristobal... See the latest NHC advisory for the forecast track of Cristobal and preferred model suite. The current official track is close to the 00z ECMWF and just a shade west of the 12z GFS through 00z Sun. The 12z NAM/UKMET/00z Canadian global are further removed from the official forecast low positions at each forecast time. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Petersen