Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 305 AM EDT Thu Aug 29 2019 Valid Aug 29/0000 UTC thru Sep 01/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Final Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non-00Z NAM blend led by the 00Z ECMWF Confidence: Slightly above average ...07Z update... Spread remains in the latest guidance across the central U.S. with the 00Z NAM continuing to stand out the greatest (see below). Adjustments by the 00Z UKMET/CMC appear to be positive although the 00Z UKMET remains flat with the 500 mb trough across the Ohio Valley. A non 00Z NAM blend of guidance with heavy weighting toward the 00Z ECMWF is preferred across the central U.S., while a general model blend can continue to be used elsewhere across the lower 48. ...previous discussion follows... The southern end of longwave troughing over the Great Lakes/Ohio Valley at the start of the period is forecast to lift northeastward through Saturday while lower amplitude longwave troughing redevelops just east of the Mississippi River Sunday morning. Meanwhile, mid-upper level ridging over CA/AZ will translate toward the Four Corners region through Sunday morning as a shortwave nears the Pacific Northwest Sunday morning. Some of the greatest differences across the CONUS are across the central U.S. are with the western end of a frontal boundary across the central Plains. A MCS is forecast to develop over eastern Nebraska/Kansas late Thursday night which has implications on the latitude of the effective front into Friday night and Saturday. The 00Z NAM is the most aggressive with the boundary sinking well south into the southern Plains. The 12Z ECMWF appears to be the most reasonable regarding run to run continuity and agreement with the latest ensemble means. At 500 mb, the 12Z UKMET/00Z GFS appear to be flatter/faster (respectively) with the corresponding trough axis Saturday morning. The 12Z UKMET appears to have convective feedback while the 12Z CMC is an outlier with its northern surface wave position through Sunday morning. Elsewhere across the CONUS, a general model blend is preferred given good agreement. ...Tropical Depression Erin... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM/UKMET/CMC closest to 03Z NHC advisory Confidence: refer to NHC ...07Z update... The 00Z ECMWF adjusted toward the weaker 00Z GFS regarding the surface low of what is currently Tropical Depression Erin. Meanwhile, westward shifts in the 00Z UKMET/CMC make these models close enough to the 03Z NHC advisory to allow inclusion as part of a blend, excluding the 00Z GFS/ECMWF. ...previous discussion follows... The 00Z GFS is a bit of an outlier with the strength of Erin through Friday depicting a weaker system relative to the remaining deterministic guidance. The 12Z UKMET/CMC are displaced east of the 03Z advisory NHC track while the 12Z ECMWF/00Z NAM are closest to NHC. ...Hurricane Dorian... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 00Z GFS/ECMWF/CMC closest to 03Z NHC advisory Confidence: refer to NHC ...07Z update... Shifts in the 00Z UKMET/CMC were slower compared to their previous cycles while the 00Z ECMWF only made minor adjustments. A blend of the 00Z ECMWF/CMC/GFS places a position nearest to the 03Z NHC advisory track for Hurricane Dorian. ...previous discussion follows... The 00Z GFS, 12Z ECMWF and 12Z UKMET are closest to the 03Z NHC advisory track regarding Hurricane Dorian through about Saturday morning. After this point in time, the 00Z GFS deviates north and west of the NHC forecast positions but the 12Z ECMWF/UKMET remain close to the NHC track. The 12Z CMC is a faster outlier with Dorian while the 00Z NAM is slower with the track. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Otto