Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 250 AM EDT Thu Jul 23 2020 Valid Jul 23/0000 UTC thru Jul 26/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 07Z update: No significant changes noted with the rest of the 00Z guidance and no changes needed to the model blend preferences. ...Broad Great Lakes trough axis and corresponding cold front impacting the OH Valley, Northeast and Mid-Atlantic into Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average Shortwave energy will brush portions of the Northeast and New England over the next 24 hours then gradually give way to zonal flow as heights build over the Central US and Mid-MS River Valley. The models show very good agreement with this synoptic pattern and evolution and a general model blend is sufficient. ...Mid-upper level troughing impacting the Northwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 24.12Z; blend of ECMWF/UKMET/ECENS after Confidence: Average A shortwave trough pushes through the Northwest this morning followed by a stronger closed low that skirts Washington State and the far northern Rockies over the forecast period. Through 36 hours, model agreement is very good and a general model blend is sufficient. Beyond that, as the closed low opens up, some timing and strength differences develop. The NAM and to some degree the GFS are the stronger solutions while the CMC is fastest and ahead of the rest of the guidance. The GFS is also a tad faster compared to the rest of the deterministic guidance and much faster than its ensemble mean. For these reasons, a blend of the ECMWF/UKMET/ECENS is preferred. ...California/Southwest U.S... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average A closed low over California will drop toward southern Nevada over the next 24-36 hours before being absorbed into the general troughing over the western U.S. into day 2/3. After the departure of the closed low from CA, another disturbance (weaker than the previous low) will reach the CA coast late on Saturday. Aside from the UKMET, the models show very good agreement in the synoptic mass fields such that a general model blend should be sufficient. ...Tropical Depression Eight... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Official NHC Forecast Best Model Proxy: 12Z ECMWF Confidence: Average NHC initiated advisories on newly formed Tropical Depression Eight as of 03Z associated with an area of low pressure currently over the central Gulf of Mexico. The latest model guidance shows fairly good agreement that this feature will move eastward over the next few days, approaching the central Texas Gulf Coast before slowing inland by the end of the period. The GFS was the most disorganized/weak with the system and wasn't considered the best proxy against the official NHC track. The remaining deterministic guidance, specifically the 12Z ECMWF, would be good proxies for model guidance. For timing purposes, the NHC track is slower compared to most of the guidance, which is a good trend considering the gradual slowing seen in the last several runs. 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 Taylor