Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 323 AM EDT Sat Aug 31 2019 Valid Aug 31/0000 UTC thru Sep 03/1200 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: Non-NAM, Non-CMC blend Confidence: Above average 07Z Update: The primary discrepancies in the synoptic pattern involve a shortwave moving into the Pacific NW on day 2 and then into the Northern Plains Monday. The NAM and CMC are now both fast outliers racing this feature eastward, far outpacing the remaining global suite. Otherwise, the models are well clustered across the CONUS. Previous Discussion: The global suite remains in good agreement in a western-ridge/eastern-trough setup through the next 3 days. While small scale perturbations in the flow will impact QPF, there is generally small spread among the majority of the models. The lone exception is the 00Z/31 NAM which becomes too fast and amplified with a shortwave moving into the Pac NW on day 2, and lifting into the northern Plains by day 3. This has the effect of pushing the associated surface low and cold front too quickly east and too sharply to the south, and for this reason the NAM is removed from the preferred blend. Otherwise, the preference this cycle includes all other available guidance, accounting for the typical biases. ...Hurricane Dorian... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Please refer to the official National Hurricane Center forecast track Initially, the GFS/ECMWF are the best proxy for the NHC track for Hurricane Dorian. However, by day 3, the GFS becomes too fast while the UKMET/ECMWF slow across the Bahamas to become more aligned with 03Z advisory positions. For this reason a GFS/ECMWF/UKMET blend is preferred to maintain integrity of the NHC track, but note more weight on the GFS the first 48 hours, trending towards higher UKMET on day 3. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Weiss