Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 148 PM EST Sun Nov 11 2018 Valid Nov 11/1200 UTC thru Nov 15/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 75% 00Z ECMWF / 25% 12Z GFS blend Confidence: Average 19Z update... Across the Northeast, the 12Z models decreased the spread with the surface low track but the 12Z NAM remains fastest. The 12Z NAM and 00Z ECMWF are farther to the west while the 12Z GFS/12Z UKMET/12Z CMC are farther east as the low moves up the East Coast. Given ensemble scatter low plot clustering is near the coast, or between the two camps but closer to the ECMWF side, a blend of the 12Z/00Z ECMWF and 12Z GFS is preferred, but with more weight on the ECMWF. Across the south-central U.S., the 12Z UKMET/CMC trended farther west with the closed low on Wednesday but the 12Z ECMWF trended east near or just ahead of the 12Z GFS. Given the diverging trends and reasoning stated below, prefer to stay the course with the preliminary preference nearer to the 00Z ECMWF but blended slightly east with the 12Z GFS. No significant changes were noted for the Pacific Northwest. ...previous discussion follows... The upper level flow across the CONUS initially features a deep layer ridge just off the West Coast with a downstream longwave trough across the central U.S. with two amplifying shortwaves diving south through the Intermountain West. Over the next 1-2 days, the mean layer troughing over the central U.S. will shift east with two components, a northern stream and a southern stream...with the southern stream getting left behind over the south-central U.S. Tuesday into Wednesday. Across the West, the northern end of ridging will be cut into by a shortwave trough Tuesday and Wednesday associated with a cold front at the surface reaching the Pacific Northwest. At the surface, a low will hug the western and central Gulf Coast tonight through Monday night at which point cyclogenesis will take place along the northern Mid-Atlantic coast. The surface low will deepen while tracking along the New England coast on Tuesday, quickly exiting into the Canadian Maritimes by Wednesday morning. Trends since yesterday have favored more separation between the northern and southern stream components of the longwave trough over the central U.S. with the GFS/GEFS representing the faster side of the spectrum. Ensemble spaghetti height plots and scatter low plots support a position nearest to the 00Z ECMWF with both the surface low tracking up the East Coast and with the southern stream closed low over the south-central U.S. 500 mb ensemble height spread is modest by 00Z/15 but shows more room to edge west of the 12Z GFS/00Z ECMWF than east. The overall model preference is to be near the 00Z ECMWF but to include a small fraction of the 12Z GFS given some of the dramatic shifts in guidance since yesterday and to avoid too much of a windshield washer effect if the models decide to trend back east/faster again. Across the Northwest, a general model blend is sufficient given differences in the surface to 500 mb pattern provide more differences in sensible weather impacts to British Columbia than Washington/Oregon. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto