Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1256 AM EDT Tue Aug 04 2020 Valid Aug 04/0000 UTC thru Aug 07/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Hurricane Isaias... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 03Z NHC advisory package Best model proxy: Multi-model consensus Hurricane Isaias made a landfall at 0310Z near Ocean Isle Beach, NC. The storm is continuing to accelerate off to the north-northeast and will be advancing up across the Mid-Atlantic coastal plain through midday Tuesday, and then crossing New England late Tuesday through Tuesday night. The 00Z NAM and 00Z GFS solutions have come in just a tad left of the 03Z NHC track, and after about 12 hours are just a tad faster as well. The 12Z non-NCEP solutions are all a tad slower and locally a tad to the right of the NHC track. However, the 00Z HRRR and 00Z HREF member suite are all a tad left of the NHC track, and especially after about 12 hours as the system crosses the northern Mid-Atlantic and moves into the Northeast. Please consult the latest NHC forecast advisory package for more details. ...Broad trough from the Great Lakes to the Gulf Coast... ...Closed low over Ontario... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average A broad trough extending from the Great Lakes down to the central Gulf Coast will be key in allowing Hurricane Isaias to lift rapidly north-northeast up along the Eastern Seaboard over the next 24 to 36 hours. The models are in good agreement in maintaining the broad trough through the period, but with some stronger northern stream energy over the Great Lakes region favoring a closed low evolution up over Ontario. The models are in good synoptic scale agreement with their mass field evolution, so a general model blend will be preferred. ...Upper trough crossing the Pacific Northwest... ...Energy dropping down over the Northern Plains/Midwest for Tuesday/Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM/GFS and 12Z ECMWF Confidence: Slightly above average An upper trough will cross far southwest Canada before then dropping southeast and digging across the northern Plains and Midwest Tuesday and Wednesday. The 12Z UKMET gradually becomes a tad weaker with the energy as it digs across the Midwest, and the 12Z CMC ends up a bit stronger and slower. The 00Z NAM/GFS and 12Z ECMWF are pretty well clustered through the period as the energy advances into the Great Lakes region and reinforces a broad trough over the region. A blend of these models will be preferred as a result. ...Southern stream trough moving into CA by Wednesday... ...Possible closed low over CA by Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in very good agreement with the initial trough coming in across CA on Wednesday, and also with reinforcing shortwave energy and possible closed low development over northern CA by Friday. A general model blend will be preferred for the time being. ...Upper trough approaching the Pacific Northwest Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average A relatively deep trough will be approaching the Pacific Northwest by late Wednesday and the models are overall in very good agreement with their timing and depth. However, the 00Z NAM is a tad on the strong side with its height falls compared to the well-clustered global models. Therefore, a non-NAM blend will be preferred with this next trough. 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 Orrison