Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1208 AM EST Sat Nov 09 2019 Valid Nov 09/0000 UTC thru Nov 12/1200 UTC ..See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... ...00Z NAM/GFS Evaluation with Preliminary Preferences and Confidence... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Weak surface low tracking north of the Great Lakes today... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above Average The guidance shows similarly with this system. ...Shortwave(s) shearing into the interior Northwest and joining with an amplifying mid-level trough axis into the north-central U.S. for Monday... ...Surface low in the vicinity of New England Tuesday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM, 00Z GFS, 12Z ECMWF blend Confidence: Average Ensemble has shown convergence over its past four 12/00Z cycles but some timing and amplitude differences remain with the 500 mb trough crossing the north-central U.S. and Great Lakes early next week. The 00Z GFS is slightly more progressive with the 500 mb trough, but flow downstream lacks a blocking ridge which may support a more progressive track to the upper trough. The 12Z ECMWF and 00Z NAM are more similar with a slower trough, NAM more amplified, but the NAM's surface low near the New England coast Tuesday morning is displaced slightly south/east of the centroid of the latest ensemble scatter low plots. The 12Z ECMWF is near the middle of the latest scatter low plots. Meanwhile, the 12Z UKMET was a bit flatter with the upper trough earlier in the period across the central U.S. and the 12Z CMC is the slowest/most amplified with the upper trough. ...Cold front nearing the Pacific Northwest on Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM/00Z GFS blend Confidence: Average Timing differences appear starting Monday morning as a cold front approaches the Pacific Northwest. The 12Z UKMET is slowest while the 12Z ECMWF is fastest with the related upper level trough. The 00Z NAM/00Z GFS appear to make up a reasonable compromise in the middle of the latest spread. ...Closed low over northwestern Mexico... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average Some minor timing differences exist with this feature with the 00Z GFS/12Z UKMET fastest and 12Z CMC slowest. Ensemble means are in the middle, and actually, the differences between the deterministic guidance are small enough through Tuesday to support a general model blend for the preference. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto