Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 108 AM EDT Fri Jul 10 2020 Valid Jul 10/0000 UTC thru Jul 13/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z NAM/GFS Evaluation with Preliminary Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-level shortwave crossing the Great Lakes/Ohio Valley through Sat... ...Associated cold front crossing the Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM/12Z ECMWF blend Confidence: Below average Run to run consistency has been poor with this system and the changes seen in the 12Z/10 ensemble spaghetti plots compared to the previous 00Z/10 cycle are dramatic valid Saturday morning. The latest consensus is near the agreeable GEFS/EC ensemble means which show the mid-level trough progressing slower than the 00Z GFS. A blend of the 00Z NAM (weaker/north) and 12Z ECMWF (stronger/south) may be the best compromise as no single model solution looks ideal here. The 12Z CMC is weaker and faster than the ensemble means with the mid-level trough while the 12Z UKMET is rather strong and north with the mid-level low center. ...Tropical Storm Fay... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM/12Z ECMWF/12Z CMC blend is closest to 03Z NHC advisory Confidence: refer to NHC The deterministic models vary with closeness to the 03Z NHC advisory for Fay over the next 48 hours. However, overall, a blend of the 00Z NAM/12Z ECMWF and 12Z CMC is nearest to the track for Fay as the storm moves into the Northeast Friday night. The NAM/ECMWF combination falls a bit west of the NHC track, and a possible over amplification of an upstream (OH Valley) trough seen in the 12Z ECMWF may be to blame as discussed in the above section. ...Mid-level shortwave to cross the northern Rocky Mountains early Friday morning, move atop the ridge and into the Upper Midwest by Sat evening, reaching the OH Valley on Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z ECMWF blend Confidence: Average The 00Z NAM/GFS are close to one another with this system as it nears the Mississippi River, but tend to be a little slower than the ensemble means. Meanwhile the 12Z UKMET/CMC are south of the ensemble means. A blend of these models may be best for this system with only the weakly defined 12Z ECMWF standing out significantly from the remaining consensus. ...Longwave trough axis moving into western Canada and the northwestern U.S. on Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average With only minor timing differences noted with a large trough axis reaching the northwestern U.S. this weekend, a general model blend will work well for the preference. 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 with the 21Z issuance: www.weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination. pdf Otto