Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 307 AM EDT Fri Aug 30 2019 Valid Aug 30/0000 UTC thru Sep 02/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Final Model Evaluation, Confidence, and Preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/CMC/ECMWF with some UKMET Confidence: Above Average through 48 hours, Slightly Below Average day 3 07Z Update: Other than the NAM, the global suite continues to be in very good agreement with the evolution of the large scale western ridge/eastern trough through Saturday. On Sunday, guidance diverges considerably with energy rotating onshore the PacNW. The GFS/CMC remain very well clustered with a slightly faster and weaker shortwave moving to the east, while the ECMWF and UKMET have shied away from their previous slower/stronger solutions to something closer to the GFS/CMC. While the highest weight in the preferred blend should still be placed on the more consistent GFS/CMC, the ECMWF and UKMET are usable for day 3. Previous Discussion: Through the first 48 hours, the guidance is in very good agreement that a broad longwave trough will persist in the east, while ridging continues in the west. Small scale disturbances within the flow may cause periodic rounds of convection of which the models differ on latitudinal placement and QPF, but really only the NAM is an outlier by being too deep with its trough. By day 3, the guidance differs considerably with handling of a mid-level trough approaching the PacNW. The NAM/UKMET close off the low to maintain a positively tilted trough axis west of the CONUS, the CMC/GFS move a weaker shortwave onshore WA/BC, while the ECMWF is somewhere in between. The differences seem to arise from vastly different jet intensities and placement as no fewer than 3 jet streaks interact over the northern Pacific Ocean. The GFS/CMC seem to handle the cross polar jet most similarly, but confidence is reduced by day 3. ...Hurricane Dorian... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Please refer to the official National Hurricane Center forecast track The guidance which most closely resembles the NHC track for Hurricane Dorian is the 00Z ECMWF/CMC which are nearly on top of the 03Z advisory points. The UKMET is in much better agreement now than its previous runs, but still slow compared to NHC and the preferred blend. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Weiss