Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 159 PM EST Fri Nov 15 2019 Valid Nov 15/1200 UTC thru Nov 19/0000 UTC A..See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Upper low over the Southeast... ...East Coast coastal low evolution... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z HREF (minus NMMB) and 00Z CMC/ECMWF blend < 36 hrs 12Z ECMWF/GEFS mean and 00Z ECENS mean blend >36 hrs Confidence: Average...becoming below average after 36 hrs An upper low deepening over the Southeast will move east and foster multiple areas of cyclogenesis off the Southeast coastline tonight through early Saturday. All of the models strongly support low pressure becoming tucked in relatively close southeast NC through this period, but thereafter, the 12Z NAM becomes an outlier in supporting low pressure remaining focused in closer to southeast NC. The global models and the hires model suite suggest the initial low center dampening out and even cyclonically looping around a new area of low pressure developing to the south along the attendant front off the Southeast coastline. Of the global models, the 12Z UKMET focuses its low pressure evolution a bit farther to the southwest and away from the model consensus which extends out through 36 hours. Meanwhile, the 12Z GFS collectively with its low centers ends up a bit farther east of this consensus. The better model clustering through 36 hours is with the 00Z CMC/ECMWF along with the 12Z ARW/ARW2 and 12Z NAM-conest. The 12Z NMMB is a northerly outlier within the hires model suite. After 36 hours, as low pressure consolidates off the southern Mid-Atlantic coastline, the 12Z GFS takes the low center northward and to the east of all of the available deterministic guidance. The 12Z NAM, 12Z CMC and 12Z UKMET end up much farther west with a more significant impact to the Northeast as the low center gets pulled in toward the coast or just offshore of New England. This cluster of solutions that tracks farther west is highly tied into there being more interaction with the upstream shortwave troughing that amplifies into the OH/TN Valleys and becomes negatively tilted across the central/southern Appalachians later Sunday and into Monday. This results in a backing of the large scale flow across the Northeast which forces the low track farther west. The 12Z ECMWF actually trended a little farther east with this latest cycle and is only a little west of the GFS solution. However, the 12Z GEFS mean and 00Z ECENS mean are very close to the deterministic ECMWF at this point. Having said that, the 12Z CMCE mean is strongly supportive of a UKMET/CMC/NAM consensus. So, there remains a divided camp with respect to the surface low evolution off the East Coast. The preference beyond 36 hours will be to lean toward a blend of the 12Z ECMWF/GEFS mean and 00Z ECENS mean at this point, with below average confidence. ...Amplifying trough across the central/eastern U.S... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend < 48 hrs 12Z ECMWF/GEFS mean and 00Z ECENS mean blend > 48 hrs Confidence: Average...becoming below average after 48 hrs A shortwave will drop southeast down across the Intermountain region and begin to amplify through Saturday. This energy will traverse the Plains/Midwest through early Sunday and then become negatively tilted by Sunday night as it crosses the OH/TN Valleys. Significant model spread exists by Monday as the energy crosses the central/southern Appalachians and Mid-Atlantic region, as the 12Z CMC/ECMWF solutions are slower than the 12Z NAM/GFS/UKMET solutions. There is some support for the slower consensus from the 00Z ECENS mean, 12Z GEFS mean, and especially the latest 12Z CMCE mean. Based on the latest ensemble guidance, and deterministic trends, a blend of the 12Z ECMWF/GEFS mean and 00Z ECENS mean will be preferred after 48 hours, with a general model blend sufficing prior to this. ...Closed low development offshore southern California on Fri... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-CMC blend Confidence: Average The models maintain the idea of a closed low developing and evolving offshore southern CA with the low dropping south to the west of the Baja Peninsula through the weekend. This system will have an interaction with T.S. Raymond over the eastern tropical Pacific as its energy and moisture will be pulled north toward the Baja Peninsula through the period. The 12Z CMC gradually becomes a bit of a westerly outlier with the evolution of the system, so a non-CMC blend will be preferred at this time. ...Upper trough arriving across the Pacific Northwest on Mon... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z UKMET/ECMWF Confidence: Average The models bring a progressive shortwave trough and associated surface low in toward the Pacific Northwest on Monday.. The 12Z NAM and 12Z GFS are on the faster side of the guidance, with the 12Z CMC/ECMWF/UKMET solutions slower. Overall, the CMC is a slow outlier. The latest ensemble suites tend to favor a solution a little slower than the faster deterministic consensus which suggests a solution toward a blend of the UKMET and ECMWF would suffice for now. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison