Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1257 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 Preliminary Evaluation, confidence, and preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/12Z CMC with some 12Z ECMWF blend Confidence: Average through 48 hours, Slightly Below Average day 3 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 12Z CMC and 00Z GFS are most closely aligned to the 03Z NHC track, but the GFS QPF seems most realistic for a tropical system in the Bahamas. The NAM/ECMWF lag the track, while the UKMET is several degrees of longitude too fast. For now then, a CMC/GFS blend is preferred for Dorian to maintain the best track integrity, with subtly more weight on the GFS. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Weiss