Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 130 PM EST Mon Jan 27 2020 Valid Jan 27/1200 UTC thru Jan 31/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Shortwave diving across the Plains to off the North Carolina coast tonight... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model Blend Confidence: Above average Guidance is in good agreement in spatial and intensity evolution of this feature as it shears off to the east today and tonight. ...Split flow trough crossing the Mountain West today and reaching the Southeast Wednesday night... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12z GFS/ECMWF/UKMET Confidence: Average 19z Update: The 12z CMC has come into a bit better agreement with the better model clustering initially, but it still becomes a pretty clear outlier by 00z Thursday with a stronger/slower wave entering the Ohio Valley. Thus would still prefer to leave off the CMC from our preferences. The 12z UKMET did trend closer to the GFS/ECMWF cluster, although is a touch slower with the trough movement. All in all think a combination of the 12z ECMWF/GFS/UKMET results in a pretty good starting point for this system...with the NAM and CMC still not preferred. The new 12z GFS has come into pretty good agreement synoptically with the 00z ECMWF with regards to how the shortwave energy within the central U.S. trough evolves as it moves into the southeastern portion of the country Wednesday night into Thursday. The 12z NAM has the same idea initially, but is overall slower than the better consensus, which eventually results in a flatter, yet more energetic wave over the southern Mid Atlantic on Thursday. Will lean against this solution at this time since the NAM pretty quickly becomes a slow outlier with this trough evolution. The 00z CMC quickly becomes an outlier with its handling of the shortwave energy over the Plains by Tuesday afternoon. Given how quick the CMC deviates from the better model clustering, would not recommend using it with this system...and would expect we will see the 12z run at least come a bit more in line with the GFS/ECMWF idea. The 00z UKMET initially looks similar to the GFS/ECMWF cluster, but ends up becoming flatter by later Wednesday into Thursday over the east. There may be some room for the GFS/ECMWF to become a bit flatter, but think the UKMET is likely too much so. Thus at this point a GFS/ECMWF blend seems to offer the best solution for this system. ...Progressive upper trough over the Pacific Northwest and amplifying into the Southern Plains Wednesday. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model Blend Confidence: Average 19z Update: The spread in the 12z suite of guidance has continued to tighten a bit over the Southwest by days 2/3. Thus a general model blend still looks in good shape. The GFS/UKMET are a bit more progressive, with the NAM/CMC/ECMWF clustered well a bit slower/south with the developing closed low. Trends suggest somewhere in the middle is the most probable outcome at this time. Yet another in a series of Pacific shortwave troughs will arrive on Tuesday across the Pacific Northwest, and then dig into the Southwest later Wednesday into Thursday. Agreement remains pretty good on the broad scale. Comparing the full suite of ensembles, the 00z ECWMF remains a bit further south with the energy by 12z Thursday, with the 00z UKMET on the northern edge of the full ensemble envelope. However neither of these solutions are different enough to be ruled out at this point. Thus in general think a general blend/consensus should work okay with this system for the time being through 00z Friday. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Chenard