Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 146 AM EST Sun Nov 10 2019 Valid Nov 10/0000 UTC thru Nov 13/1200 UTC ..See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... ...00Z Model Evaluation with Final Preferences and Confidence... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Amplifying mid-level trough axis into the north-central U.S. for Monday... ...Surface low in the vicinity of New England Tuesday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 00Z UKMET blend Confidence: Average ...07Z update... The 00Z suite of deterministic guidance is in good agreement now regarding the shortwave trough and surface low track. While the 00Z UKMET adjusted favorably with respect to its previous 12Z cycle, the UKMET remains a bit more progressive and offshore with the surface low near New England than ideal. A non 00Z UKMET blend is preferred to smooth out remaining smaller scale differences. ...previous discussion follows... There is good agreement with the upper trough amplitude and timing as it nears the Great Lakes region with minor differences showing up after Tuesday morning. The 12Z UKMET is flatter and faster with the shortwave, resulting in an eastward displaced surface low early Tuesday. Meanwhile, the 12Z CMC becomes slightly slower/deeper with the upper trough placement resulting in a surface low displaced to the south a bit of the agreeable 00Z NAM, 00Z GFS and 12Z ECMWF. The good agreement with the surface low among the 00Z NAM/00Z GFS/12Z ECMWF is broken up by the 18Z and 12Z GEFS/12Z ECMWF mean surface lows displaced slightly south and east of the deterministic consensus. Therefore, blending the NAM/GFS/ECMWF with the 12Z ECMWF mean is preferred to account for the displacement of the means relative to the deterministic agreement. ...Cold front nearing the Pacific Northwest on Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 00Z UKMET blend Confidence: Slightly above average ...07Z update... Ensemble spaghetti plots at 500 mb, showing the 546 dam line indicate the somewhat stronger 00Z ECMWF/CMC and 00Z NAM models are on the stronger edge of the majority of members. However, the run to run consistency of the ECMWF and CMC can't be ignored. For now, a blend of the somewhat flatter 00Z GFS with the more robust 00Z ECMWF/CMC is preferred with the 00Z UKMET faster and flatter at 500 mb. ...previous discussion follows... Cold frontal timing into the Pacific Northwest is good with the latest guidance. Differences show up with the corresponding shortwave downstream into the north-central U.S. The 12Z CMC stands out with a stronger/faster shortwave while the 12Z UKMET is weaker by 12Z/13. A blend of the 00Z NAM, 12Z ECMWF and 00Z GFS is reasonable given better agreement to the ensemble means. ...Closed low over northwestern Mexico... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 00Z UKMET blend Confidence: Average ...07Z update... Only the 00Z UKMET remains as a faster outlier regarding the 500 mb low track across northwestern Mexico. Strong ensemble support for a slower, non-UKMET track, leaves the 00Z UKMET an unlikely pick for this system. The preference is for a non-00Z UKMET blend. ...previous discussion follows... Ensemble spread is modest by 12Z/13 but the 12Z CMC is slower and 12Z UKMET faster than the middle of the spread. The middle of the spread, tighter clustering and ensemble means supports a blend of the 00Z NAM, 00Z GFS and 12Z ECMWF. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto