Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 236 AM EDT Thu Apr 26 2018 Valid Apr 26/0000 UTC thru Apr 29/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z model evaluation including final preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-level shortwave lifting north along the New England coast today, interacting with a northern stream shortwave crossing the Great Lakes... ...Surface low departing from the Northeast today/tonight... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show similarly with this system. ...Mid-level energy departing from the lower MS valley this morning and crossing the Southeast by Friday... ...Low pressure lifting from the Southeast to the Northeast Friday and Saturday... ...Phasing with northern stream energy over the Northeast by Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average The 00Z UKMET/CMC trended more west with the track of a surface low as it moves through the Mid-Atlantic region early Friday, and are now closer to the previous preference of the NAM/GFS/ECMWF. The 00Z ECMWF nudged slightly in the direction of the 00Z NAM/GFS but minor differences remain. Regarding the phasing energy over the Great Lakes/Northeast for the weekend, there continues to be convergence with subsequent model cycles as seen with the previously faster 12Z ECMWF having adjusted slower with its 00z run toward the 00Z NAM/GFS. Similarly, the 00Z UKMET and CMC now look closer to the previous preference, such that a general model blend can be used for this system. ...Positively tilted upper level shortwave crossing the upper MS valley and central Plains today, with the southern portion of the trough reaching the eastern Gulf Coast Friday night... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average The models only show minor placement differences, with a blended approach yielding a solution near a blend of the ensemble means. Given differences are small, a general model blend can be used for this system. No significant differences were noted with the 00Z ECMWF/UKMET/CMC relative to their 12Z cycles. ...Closed low evolution toward the West Coast by Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM, 00Z GFS, 00Z ECMWF blend Confidence: Average Good agreement exists with this system until late Saturday, when the 00Z UKMET/CMC depict a sharper mid-level trough axis over the West, while also being displaced toward the southern side of the deterministic spread. The 00Z GFS is a bit faster to move the upper trough to the east, while the 00Z ECMWF/12Z ECMWF mean a bit slower. Ensemble spread is modest for the day 3 time frame, but it appears a blend of the 00Z NAM/GFS/ECMWF is closest to the middle of the ensemble spaghetti plots, versus the farther south 00Z UKMET/CMC. ...Weak southern stream shortwave ejecting out toward the southern High Plains by Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM, 00Z GFS and 00Z ECMWF Confidence: Slightly above average The models eject a weak southern stream shortwave out of the Southwest and toward the southern High Plains by Saturday. The 00Z CMC and especially the 00Z UKMET are a bit stronger and better defined with the energy as it ejects out across eastern NM and western TX. The 12Z UKMET is a near outlier with respect to the latest ensemble spaghetti heights at 500 mb Friday evening, but the 00Z UKMET did trend a bit weaker, while continuing to lie on the stronger edge of the available ensemble guidance. The 00Z NAM, 00Z GFS and 00Z ECMWF are all a bit weaker and sheared in their appearance, and fit better into the ensemble clustering. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto