Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1255 PM EDT Mon Oct 07 2019 Valid Oct 07/1200 UTC thru Oct 11/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Upper trough crossing the Great Lakes/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show very good agreement with the details of the upper trough and associated shortwave energy crossing the Great Lakes and northern New England today through Tuesday. A general model blend will be preferred. ...Energy amplifying over Central Appalachians/Mid-Atlantic... ...Deepening surface low pressure off the East Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z UKMET/06Z GEFS/00Z ECENS mean Confidence: Slightly below average The guidance again shows shortwave energy advancing across the mid-MS and OH Valleys that will break away from the westerlies and amplify toward the central Appalachians through Tuesday, with at least a weak mid-level closed low evolving near the northern Mid-Atlantic region by Wednesday. On Thursday, the models support the closed low feature being generally southeast of Long Island. The 12Z NAM/00Z UKMET and 00Z ECMWF are the strongest solutions, followed by the modestly weaker 12Z GFS and 00Z ECMWF. This energy is expected to interact with an area of disturbed weather northeast of the Bahamas that will be lifting northwest to offshore of the Carolinas on Tuesday. The guidance is in very good agreement in depicting offshore cyclogenesis as the upstream height falls approach the East Coast. There remains a fair amount of latitudinal spread in the guidance with where this secondary cyclogenesis will focus, as the 12Z NAM/00Z CMC solutions are clustered farther north, and the 00Z ECMWF farther south. The 12Z GFS and 00Z UKMET are overall splitting the difference between camps. The 06Z GEFS mean favors the GFS solution, with the 00Z ECENS mean siding with the ECMWF, which suggests the NAM/CMC solutions are likely a tad too far north through the period. A compromise between the ensemble means will be preferred, along with the UKMET which collectively appear to approximate the model consensus with this system. Confidence remains rather limited given the level of ensemble and deterministic model spread with this system. ...Weak surface low pressure impacting the FL Peninsula... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Meanwhile, a separate area of disturbed weather associated with a tropical wave/surface and weak area of low pressure will be advancing west across south Florida today and tonight which will advance into the eastern Gulf of Mexico on Tuesday before weakening and losing its identity. A general model blend can be preferred with this system. ...Deep upper trough/closed low amplifying over the West... ...High Plains cyclogenesis... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS/00Z UKMET and 00Z ECMWF Confidence: Slightly above average The models are in very good agreement on amplifying a northern stream trough down toward the Pacific Northwest, northern Rockies and northern High Plains later today and which will send a very strong cold front southeast from Canada along with much colder air. As the cold front advances southeast, one wave of low pressure will develop along it over southeast MT by late Tuesday which will cross the Dakotas through early Wednesday before then dampening out. The models show excellent agreement with this evolution. Then as the cold front advances down the Front Range of the Rockies by late Wednesday, a new area of strong cyclogenesis is expected to take place over eastern CO which will then advance east and elongate along the front on Thursday as it crosses the central Plains. The 12Z NAM gradually becomes a bit stronger than the global models with its depth of the trough and closed low over the Intermountain West by late Wednesday and Thursday. The 00Z CMC by the end of the period appears to be placing the core of its height falls a bit too far north over the northern High Plains as the guidance suite supports a consolidation of mid-level energy farther south closer to the central Rockies. The CMC as a result ends up being a bit more progressive with its cold front late in the period and more out of phase compared to the other models. The better model clustering and ensemble support at this point favors a blend of the 12Z GFS/00Z UKMET and 00Z ECMWF, and so a blend of these solutions will be preferred. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Orrison