Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 250 AM EDT Fri Aug 02 2019 Valid Aug 02/0000 UTC thru Aug 05/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation and Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Central U.S... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of GFS/ECMWF Confidence: Average The models show the energy dropping down across SD/NE tonight through midday on Friday and then across eastern KS Friday night and early Saturday. The 00Z UKMET is the weakest of all of the guidance with the 700 mb energy as it drops down the east side of the ridge axis. The 00Z NAM is the most intense and has a deeper 700 mb low than the other models. This may be due to convectively-induced grid scale feedback. The NAM track of the 700 mb wave is comparable to other guidance, but needs to be weakened. ...Northeast U.S./upper Ohio Valley/northern mid Atlantic... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly Above Average Across the Northeast down through the lower lakes, upper Ohio Valley, and northern Appalachians, heights gradually lower with time this weekend. The NAM/GFS and SREF/GEFS Means cluster well across the region. The 00Z ECMWF was not quite as flat as the solution it offered at 12Z on Thursday...but it was still an outlier compared to other guidance...and was preferred less than the other guidance based on teleconnections with the southwest closed low. ...Pacific Northwest/Southwest Canada... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z CMC/UKMET/ECMWF Confidence: Slightly Above Average The guidance agrees in taking a positively tilted longwave trough across southwest British Columbia, Vancouver Island, and off the northwest coast and moving the wave northeast into central Canada over the weekend. The models indicate a 700 mb shear axis remains off the WA/OR coast that persists and eventually develops into a second closed low Sunday. The 00z NAM trended west to join the primary cluster of models, so now can be considered part of the preferred blend. The latest ensemble means per the GEFS mean and ECENS mean are supportive of the operational models. The 21z SREF Mean was on the eastern edge of the suite of solutions and therefore least preferred, given the downstream blocking high limiting forward motion. ...Upper trough over the Gulf Coast/Southeast... ...Wave axis impacting Florida... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM/UKMET/ECMWF solutions Confidence: Average A broad upper trough over the Gulf Coast states will gradually drift west over the weekend. The mid level circulation and surface wave near south Florida move northeast ahead of the upper trough across the southeast coast and then off the coast this weekend. The 00z NAM was a little stronger with the 700 mb low and seems to match the circulation seen on radar and satellite. The GFS was a tad more amplified than the non-NCEP guidance with this troughing, with the UKMET deamplifying it faster. The 00z UKMET and 12z Canadian were least preferred given teleconnections favor a persistent higher amplitude trough. Regarding the surface trough impacting Florida, the guidance is gradually supporting development of a weak low center along this as it lifts northeast up off the Southeast coastline this weekend. The 00Z NAM became the strongest solution as the low moves off the mid Atlantic coast. Given most solutions shear the 700-850 mb circulation, a blend of solutions should suffice. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Petersen/Bann