Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1244 AM EDT Sat Sep 29 2018 Valid Sep 29/0000 UTC thru Oct 2/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Initial Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Preference for the Entire CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: ECMWF/GFS/CMC blend Confidence: Slightly above average Hurricane Rosa Proxy: 18Z GEFS mean The large planetary scale upper trough over the northern U.S. and much of Canada Saturday morning is expected to evolve into a more quasi-zonal flow pattern from the Rockies to the Northeast U.S. by Sunday. A potent shortwave trough will cross southern Canada with a second trough building across southwestern Canada by Monday afternoon and into Tuesday. The rex block breaks down over the eastern Pacific and the first upper low reaches the Oregon coast Saturday night and then becomes absorbed into the westerlies. A second closed low will likely approach the California coast by Tuesday as a West Coast trough becomes more amplified. A broad upper level trough is expected to continue from the southern plains to the Southeast U.S. through the weekend and into early next week whilst tropical cyclone Rosa makes its way to the Southwest U.S. There is good overall agreement in the models through at least Sunday evening, after which some relatively minor differences begin to emerge. The NAM is slightly more amplified with the weakening initial closed low that reaches Oregon and evolves into a trough. The GFS is slightly more progressive with the first shortwave trough crossing Ontario and Quebec on Sunday. The UKMET indicates more upper level ridging across the Ohio Valley and also the Great Lakes compared to the model consensus. Regarding Hurricane Rosa and its eventual path, the 18Z GEFS mean position represents the model closest to the NHC track. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml D. Hamrick