Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 213 AM EST Wed Jan 22 2020 Valid Jan 22/0000 UTC thru Jan 25/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Final Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ ...Closed low off the Southeast coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: Non-NAM blend Confidence: Above average Closed vertically stacked low east of Florida will move eastward away from the coast through tonight. Subtle vorticity lobes rotating around the main closed feature will allow surface troughiness to persist towards the FL coast much of today, but any significant sensible weather impacts will remain offshore. The NAM is most aggressive with lagging mid-level energy, keeping the trough in place longer and driving a deeper surface trough. This is clearly the outlier and not-preferred for the blend. ...Shortwave moving from New Mexico towards the Gulf Coast tonight... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~ Preference: Non-NAM/UKMET blend, CMC is a reasonable surface proxy Confidence: Slightly above average Shortwave and accompanying weak surface low will dive southeast from New Mexico this morning to the Louisiana Gulf Coast tonight, before becoming absorbed in the large mid-level vortex developing on Thursday. The overall amplitude of both the mid-level features and at the surface is weak, and there is good agreement in the evolution among the various global models. The exception the NAM being a fast outlier digging the shortwave southeast, and the 00Z UKMET became much stronger than the remaining consensus. The ECMWF has good support from its ensembles, and the GFS has its own ensemble support, with some latitudinal differences separating the two camps. The CMC is nearly in the middle of this clustering, such that a blend of the ECMWF/ECENS/GFS/GEFS would lead to a solution likely close to the CMC, which is the preferred operational guidance. ...Trough moving onshore the Pacific Northwest Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~ Preference: 00Z ECMWF/UKMET, 12Z ECENS Confidence: Average A piece of energy shedding from a closed low near the Gulf of Alaska will eject eastward into the Pacific Northwest on Friday, accompanied by an intensifying, although still modest, Pacific Jet streak bringing heavy rainfall to the Northwest. The NAM continues to be exceptionally flat with its amplitude of this feature compared to the global consensus, likely due to a weaker anticyclonic jet streak and lagging more residual energy back into the main trough. There is a clear dichotomy between the NCEP and Non-NCEP camps with respect to the intensifying jet streak, with the NCEP camp weaker and slower. The Non-NCEP solution seems more reasonable. From the remaining guidance, the CMC squelches the mid-level energy very quickly as it moves onshore, which seems unlikely in the presence of continued jet dynamical lift. This leaves the ECMWF/UKMET as the most agreeable and reasonable solution, with support from the ECENS mean creating the preferred blend. ...Binary interaction of closed lows Thursday-Friday in the Plains and Missouri Valley... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: 00Z NAM/CMC/ECMWF, 12Z ECENS Confidence: Slightly below average Still many details to iron out with two mid-level impulses moving through the Plains today into Thursday, and how they will deepen/interact through the rest of the week. The GFS over the past several runs continues to exhibit minimal run-to-run consistency, leaving little confidence in its evolution. Multiple features interacting create lower than usual confidence, but the leading shortwave should eventually become dominant and intense, especially late on D3 /Friday night/ across the Missouri Valley and into the Ohio Valley. This should lead to strong cyclogenesis along a triple point across the Mid-Atlantic D3, with this triple point extending from a primary surface low beneath the trailing upper trough over the Upper Midwest. Moisture drawn northward ahead of this system could be significant. The NAM/ECMWF/ECENS are in good agreement through 60 hours, with the CMC becoming aligned thereafter despite being slightly too fast/south Days 1-2. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Weiss