Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 231 PM EDT Sat May 19 2018 Valid May 19/1200 UTC thru May 23/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z model evaluation...with final preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Broad upper trough and embedded MCVs over the East through Sunday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show similarly with this system. ...Upper trough crossing the upper Midwest today/tonight... ...Cold front/surface wave crossing the Great Lakes/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show similarly with this system. ...Upper trough/closed low over the central Plains today and crossing the Midwest by Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS/12Z ECMWF Confidence: Slightly below average Convergence continues with this system aloft, but detail differences remain both aloft and at the surface. The 12Z NAM is slowest with the 500 mb reflection of the shortwave while the 00Z ECMWF is fastest with the leading edge of the mid-level wave. The 12Z ECMWF slowed down relative to its previous cycle, such that better agreement is seen in the 12Z deterministic model suite. At the surface, the ensemble means agree best with a 12Z GFS/12Z ECMWF blend with the 12Z UKMET/CMC suppressed/weaker/south with the main surface low tracking into the Ohio valley. Given the weak nature of the system as it moves east, detail differences continue to make for a below average confidence level. ...Upper trough digging into the West on Sunday... ...Closed low digging into the Southwest Monday and Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show remarkable agreement with this system through the short range period with little overall spread in the deterministic/ensemble guidance. Some minor timing differences show up by 00Z/23Z, but spread is small enough at this time to prefer a general model blend. ...Mid level trough developing over the eastern Gulf of Mexico by Sunday... ...Lifting up across the Southeast on Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z CMC blend Confidence: Average The models develop a weak mid level trough and possible closed low over the eastern Gulf of Mexico along with a weak surface low/wave by late Sunday which then lifts up across the Southeast on Monday. The 12Z ECMWF trended toward the consensus regarding the strength of the low-mid level reflection of this system compared to the weaker 00Z ECMWF. The ensemble scatter low plots continue to show very little support for a defined surface low, but none of the deterministic guidance shows a closed isobar around their surface low forecasts. Therefore...will prefer a consensus approach excluding the 12Z CMC given the CMC is much quicker to thrack the low to the north compared to the remaining available guidance. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto