Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 256 PM EDT Wed Oct 10 2018 Valid Oct 10/1200 UTC thru Oct 14/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Final Model Evaluation...with latest preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z ECMWF/UKMET/CMC Confidence: Slightly above average A large scale trough over much of the central and western U.S. and an East Coast ridge at the beginning of the forecast period Wednesday is forecast to slowly translate eastward over the next few days as the western Atlantic ridge retreats farther offshore. The leading edge of the height falls across the Ohio Valley and Great Lakes will be accompanied by a strong cold front and surface low that will herald a significant pattern change for the eastern U.S. There is very good model agreement on the timing of the front and the passage of the strong surface low across the Great Lakes, so a general model compromise can be incorporated with that system. In the wake of the upper Midwest trough and surface low, there will be a pair of shortwave troughs tracking southeast from central Canada, with one crossing the northern Plains and Midwest through Friday night, and then reaching the East Coast by Saturday afternoon. The second shortwave will then amplify down across the northern High Plains by Saturday night. The 12Z ECMWF is now closer to the model consensus and the GFS faster with the first shortwave, and the NAM becomes a strong and faster outlier with the second shortwave, similar to its earlier runs. Across the West Coast, the guidance continues to support a closed low evolving off the central California coast by Friday morning and continuing through Saturday evening. The 00Z NAM continues to retrograde more energy off to the west compared to the global models. Based on the latest model spread and clustering of solutions across the continental U.S. for this period, a blend of the 12Z ECMWF/12Z UKMET/12Z CMC is preferable as a starting point in the forecast process. ...Hurricane Michael... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: See the latest NHC forecast advisory Powerful Hurricane Michael will lift north and be crossing southern Georgia within the next 12 hours, and will then rapidly recurve northeastward across the interior of the Carolinas and the southern Mid-Atlantic states through the 36 hour time-frame. The 12Z ECMWF is close to the model consensus through 18Z Thursday, and then becomes slightly slower. Thereafter, as the storm exits the Mid-Atlantic coast, the ECMWF and especially the 00Z EC mean are on the slower side of the guidance. Meanwhile, the 12Z UKMET is the fastest solution with the track of Michael once it reaches the Mid-Atlantic region. The 12Z ECMWF and GEFS mean are closer to the NHC track for Michael. ...Hurricane Sergio... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: See the latest NHC forecast advisory The global models all continue to indicate Hurricane Sergio tracking off to the northeast toward the central Baja California peninsula over the next couple of days, with the storm likely making a landfall on Friday. Thereafter, the storm will begin to lose its identity and intensity as it traverses northwest across mainland Mexico, but its moisture and remnant mid-level energy will impact portions of the Southwest and also the southern Plains. The 12Z GFS is the fastest solution to make landfall, whilst the CMC and the EC mean are on the slower side of the guidance. The 12Z UKMET and ECMWF are closer 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