Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 118 PM EDT Sat Oct 26 2019 Valid Oct 26/1200 UTC thru Oct 30/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS Evaluation with Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Amplified trough/closed low lifting toward the OH Valley... ...Post T.C. Olga... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in good agreement with this system, so a general model blend will be preferred. ...Deep trough digging across the Intermountain West on Sunday and reaching the Plains on Monday... ...Weak surface wave tracking across the Midwest Monday night with trailing cold front... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z ECMWF, 12Z NAM and 00Z UKMET Confidence: Average Differences with the mid-level trough's progression out West begin to become more significant early Monday with timing issues concerning ejection of the shortwave into the central Plains. The 12Z GFS is fastest, and has been with similar systems in the eastern Pacific ridge/western CONUS trough pattern of late. Ensemble trends through Tuesday morning have been slower with the GEFS toward the more consistent ECMWF ensembles. Prefer to stay near the ECMWF ensemble mean or perhaps a shade faster which is close to a blend of the 00Z ECMWF, 12Z NAM and 00Z UKMET. ...Shortwave/clipper low over MT/ND by Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average Any model differences with this system are minor enough to support a general model blend. ...Closed low likely setting up over the Intermountain West for Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z NAM, 00Z ECMWF and 00Z CMC Confidence: Average Similar to previous systems digging into the West that we've seen recently, the 12Z GFS is the farthest east with a likely closed low over the Great Basin on Tuesday. Trends in the GEFS and GFS support a slower/more westward shift over the past four 12Z/00Z cycles. Currently, near the ECMWF mean and 00Z ECMWF appears like the most favorable position, with the 12Z NAM and 00Z CMC the next closest models to that position. A 3-way blend between the 00Z ECMWF, 12Z NAM and 00Z CMC is preferred at this time. ...Potential disturbance in the Gulf of Mexico early next week... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Below average There is currently an enhanced area of disturbed weather south of Cuba which some of the models track around the western side of the subtropical Atlantic ridge into the Gulf of Mexico. Deep moisture in place with this area of disturbed weather will join with an axis of high moisture out ahead of the tail end of a cold front which will be crossing the East Coast on Sunday. There are varying solutions seen in the latest deterministic guidance through Tuesday morning, but for now, the preference will be for a general model blend and downplaying anything more organized in agreement with the latest thinking from the NHC. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Otto