Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1155 AM EST Tue Nov 12 2019 Valid Nov 12/1200 UTC thru Nov 16/0000 UTC ..See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Departing East Coast storm system today/tonight... ...Upper trough pivoting through the Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average No significant differences are noted in the guidance with the departing New England low center, and cold front exiting the East Coast. The models are also in good agreement with the details of the deep upper trough pivoting through the Northeast through early Wednesday, so a general model blend will be preferred. ...Shortwave tracking from the Northwest to the Plains by Wed... ...Closed low development over the Southeast... ...Cyclogenesis off the Southeast Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 48 hours 12Z GFS...after 48 hours Confidence: Above average...becoming below average after 48 hours The models show good agreement with the details of the shortwave crossing the Pacific Northwest and digging southeast across the Plains through Wednesday. On Thursday, this energy will begin separate out from the westerlies and dig down across the lower MS and TN Valleys. As this energy drops southeast across the Gulf Coast states, it should interact with and capture energy associated with an ejecting southern stream closed low crossing from Mexico through south Texas and the western Gulf of Mexico. The result of this interaction will ultimately be a closed low over the Southeast by Friday, with coastal cyclogenesis taking place just southeast of the Carolinas. The 12Z NAM overall appears to be a bit too strong with its shortwave amplification down across the TN Valley and Gulf Coast states. Meanwhile, the 00Z ECMWF appears to be too slow with its progression and is the slowest deterministic solution with the closed low. The 00Z CMC is a weak outlier aloft and at the surface as the system reaches the Southeast. The 12Z GFS and 00Z UKMET show the best clustering aloft and more closely approximate the model consensus, but at the surface, the UKMET appears to be too far south with its coastal cyclogenesis. There is a bit of spread among the ensemble suites with the placement of the coastal cyclogenesis, but overall the GFS has the better support at the end of the period. Will prefer a general model blend through 48 hours, followed by a solution toward the GFS thereafter. ...Mid-level shortwaves approaching the West Coast on Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average A relatively weak mid-level shortwave is expected to approach the Oregon/California coastlines early on Thursday while a second shortwave lurks to the north with a likely destination of Washington/British Columbia Thursday night. Despite some minor timing differences of these two features, agreement is good enough to warrant a general model blend which aligns with the latest ensemble means. ...Closed low development offshore southern California on Fri... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS, 00Z UKMET and 00Z ECMWF Confidence: Average Additional shortwave energy approaching California late Thursday will break away and dig southeast to offshore southern California on Friday, with the guidance supporting a weak closed low evolution. The 12Z NAM is a weak and more progressive outlier compared to the global model suite. Of the global models, the 12Z GFS, 00Z UKMET and 00Z ECMWF show the best model clustering, and have support from the 00Z ECENS mean. Therefore, a blend of these solutions will be preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison