Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 108 PM EDT Thu Jul 23 2020 Valid Jul 23/1200 UTC thru Jul 27/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z NAM/GFS Evaluation Including Preliminary Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Broad Great Lakes/Northeast trough axis and corresponding cold front impacting the OH Valley, Northeast and Mid-Atlantic into Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The models show similarly with this system. ...Mid-upper level troughing tracking from the Northwest into the north-central U.S. through the weekend... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/00Z ECMWF blend Confidence: Average A mid-level closed low/shortwave trough will track through southwestern Canada Friday and Saturday with a cold front leading at the surface and extending into the northwestern U.S. The model agreement is fairly good through Saturday but the 12Z NAM begins to show up as fastest with the speed of the mid-level trough by late in the day. The 00Z UKMET/CMC appear slower than the consensus on Sunday. While the timing differences are not large and model-driven convective boundary ahead of the main front could be more significant. it seems the 12Z GFS and 00Z ECMWF represent the best ensemble clustering which lies in the middle of the deterministic spread. ...California/Southwest U.S... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non-00Z CMC blend Confidence: Average After the departure of a small closed low from CA tonight, another disturbance (weaker than the first) will reach the CA coast late on Saturday. Aside from the 00Z CMC, which is displaced farther south and is faster beginning on Sunday, the models show very good agreement in the synoptic mass fields such that a non 00Z CMC blend can be used for this system. ...Tropical Depression Eight... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Official NHC Forecast Best Model Proxy: 12Z NAM/00Z ECMWF blend Confidence: refer to NHC products The 15Z NHC advisory for Tropical Depression Eight is in general agreement with the . The latest model guidance shows fairly good agreement with the latest model guidance. However, none of the deterministic models match exactly with the NHC track for all of the next 3 days. There are differences with organization of the mid-level energy aloft as well. NHC strengthens T.D. Eight into a weak tropical storm by Friday morning and maintains a weak intensity until landfall when the system weakens back below tropical storm status. Given the track and intensity forecasts by NHC, a blend of the 00Z ECMWF and 12Z NAM appears to be the closest proxy to the 15Z NHC advisory. The 00Z UKMET is the strongest while the 12Z GFS is weakest. The 00Z CMC is the farthest north with the low track. For the latest official guidance, see the most recent advisory from the National Hurricane Center. 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 Otto