Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 235 PM EDT Fri Jun 05 2020 Valid Jun 05/1200 UTC thru Jun 09/0000 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ---Amplifying wave shifting east across Ontario through tonight and northern New England Saturday night... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General blend becoming non-CMC blend after 48hrs Confidence: Slightly above average 19z update: The CMC is a bit slower, broader and further west enough to suggest its removal after 48hrs...7.12z. Confidence remains slightly above average ---Prior Discussion--- WV suite denotes a strong jet streak over the northern Plains into the Western Great Lakes, with an W-E elongated shortwave rotor to its north. This wave along with the jet support buckles and amplifies through the Great Lakes, Ontario later today leading to a solid positively tilted trof to progress through the Northeast late Sat and digging through the Mid-Atlantic by early Sunday. Models continue to come into tighter overall agreement and while there remains a small amount of spread/difference (GFS/CMC) in the mass fields, a general model blend can be preferred at slightly above average agreement. ...Initial cut-off low offshore southern California, moving onshore tonight, into Great Basin Saturday, the Wyoming Rockies Saturday night, and the northern Plains Sunday. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model Blend Confidence: Slightly above average 19z update: There was little significant change in the 12z ECMWF/GEFS/CMC or UKMET to deviate from initial preference, perhaps providing increased confidence overall. So will continue with a general model blend at slightly above average confidence. ---Prior Discussion--- GOES-West WV suite denotes a dry closed low with excellent jet/downstream diffluence across the Desert Southwest. Convective development across the high terrain later tonight into tomorrow morning leads to some mild disruption of the wave as a whole (expanding it downstream). The 12z NAM is most disrupted and starts to accelerate into the northern High Plains much faster than other guidance; once there, the approaching closed low (see section below) interacts and further amplifies the wave making the NAM solution a bit less tolerable in the overall suite, particularly with upper level support/features. The 12z GFS is also a bit fast and more amplified, particularly as the upstream closed low approaches. The 00z CMC is the other side of the spectrum, slower, accompanied by the ECMWF. Still, the spread/timing is small enough to continue to favor a more centralized solution (close to the placement/timing of the ensemble suite)...and so a general model blend is preferred at slightly above average confidence. ...Closed low off British Columbia drifting south through Friday night and then off Washington/Oregon Saturday, moving east and onshore Saturday night-Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model Blend Confidence: Slightly above average 19z update: Further separation occurring in timing with the UKMET/ECMWF/CMC trending closer toward consensus while the GFS/NAM are more agreeable, with the bulk of modal differences occurring with the interaction/amplification of the precursory wave across Southern Canada bleeding into MT. Still, the affects in the lower levels/surface a still small enough to support the general model blend but confidence is reduced to slightly above average. ---Prior Discussion--- Well defined symmetric closed low in the Southern Gulf of AK is well forecast through the short-term as it makes landfall into the Pacific Northwest through the weekend. The uncertainty arises as the central core enhanced by the Pacific jet rounds the broadening base into the Snake River Valley/Great Basin and begins to interact with the exiting shortwave lifting through the northern Plains. Still, most of the uncertainty comes with differences in timing within the guidance suite and therefore the magnitude of amplification with the precursory wave moving into SW Canada. The GFS is most aggressive and swings the jet through WY into MT stronger and faster. It is supported by the 12z NAM but both have shown this to be a bit too fast. The ECMWF/CMC are equally problematic but on their typical slower trend side; while the UKMET is most central. All in all, a blend of the solutions or a hedge toward the central UKMET is preferred but confidence remains above average in this general model blend preference. ...Cristobal... ~~~~~~~~~~~~~~~~~~ Preference: 03Z NHC advisory Best Proxy: 12z UKMET/ECMWF blend Confidence: Refer to NHC products 19z update: The ECMWF shifted a bit faster and stronger and while initially a bit slower than the official forecast, it matches very well nearing the LA coast and thereafter to suggest a best proxy is a combination of the 12z UKMET/ECMWF blend. ---Prior Discussion--- The official track for T.D. Cristobal is a good of compromise of non-GFS 00Z global guidance with best timing looking most like the 00z UKMET. The 12z GFS continues to be well north and east of the remaining global guidance with the bulk of GEFS solutions though even they are slower than the operational. By the end of Day 2, the 12z NAM is shifting a bit west of the remaining cluster and the 00z CMC is remarkably weak and diffuse (particularly in the mid to upper levels relative to the remaining guidance and even the outlying GFS/NAM as it lifts north. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina