Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 146 PM EST Fri Jan 11 2019 Valid Jan 11/1200 UTC thru Jan 15/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Central and Eastern US system... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Slightly above average 19z update: The 12z ECMWF shifts to a more amplified northern stream, which helps to lift the developing coastal low a bit north and rapidly develop the cyclone along the Gulf Stream into the NW Atlantic, south of the over-amplified NAM but slightly faster/north of the GFS. The 12z CMC and UKMET both joined it...and along with the GFS support a slightly above average confidence in a non-NAM blend. The most significant remaining spread is located in the languishing deformation trof across the OH/TN valley and while not insignificant, the non-NAM blend will likely suffice for sensible weather fields as well. ---PRIOR DISCUSSION--- Smaller scale internal shortwave/latent heat release interactions continue to lead to run to run variation in the overall model suite, impacting sensible weather setup though the overall synoptic pattern is showing increased agreement. The 00z ECENS members shifted a bit faster with increased southern stream interaction leading the wave to be a bit more compact than yesterday's 12Z, with the 00z operational run on the faster side shifting east with time. This is in line with the trends of the NAM and UKMET, but interestingly the ECMWF is fast/flatter with northern stream shortwave crossing New England, opposed by the NAM/GFS. While the 06z NAM was significantly over-amplified, developing a strong, north surface coastal low. The 12z NAM has backed off in the northern stream, but continues to be faster/compact in the southern stream to develop a deeper surface wave still on the northern side of the deterministic and even ensemble cluster. The 12z GFS is more middle ground between the NAM/ECMWF, but has also trended a bit slower to match more ECMWF/UKMET. With the departure of the 00z ECENS mean/ECMWF, the 00z CMC and CMCE look very slow exiting the trof, and is less robust with the warm advection QPF across the Ohio valley and is most evident maintaining strength of the shortwave out of the Pacific stream under the Rex block. All in all, there remains moderate to high internal smaller scale variation lending to some increased uncertainty though the larger scale pattern/track and evolution is consolidating around the ECMWF/ECENS with some GFS with some lower inclusion of the UKMET. Confidence is average to slightly above average. ...Western US... ~~~~~~~~~~~~~~~~~~ Preference: 12z ECMWF/UKMET/GFS blend Confidence: Slightly above average 19z update: Now that the surface cyclone has developed off the West Coast, the remaining non-NCEP guidance (UKMET/CMC) have come into much more agreement as it lifts north like the ECMWF/12z GFS. While the CMC continues to depict reduced binary interaction with the next approaching system, the UKMET and ECMWF both shifted toward the GFS supporting a more elongated/stretched solution, which seems more likely given shape/evolution of the block over the NW US states. The 12z UKMET is a bit faster than the ECWMF/GFS in opening up into the stretched NW-SE wave, but the better agreement provides increased confidence in a 12z GFS/ECMWF/UKMET blend (slightly above average). ---PRIOR DISCUSSION--- Omega block setup in the NV Great Basin to E WA, will be undercut by strong shortwave later today into tomorrow, with fairly good model agreement with the timing of the front/moisture plume into S CA and into AZ/NM has it breaks down. The 00z ECMWF is a bit wetter and slower while the UKMET is a shade north, but still quite good agreement to have good confidence with this system. Though the northern portion of the elongated trof (given the strength of the block) still is yet to fully resolve the developing surface low just W of the 40N130W benchmark, with sizable shifts toward slower, deeper solution lifting north. The ECMWF has shifted to this positions steadily for the last few days but the GFS shifted away and has come back toward a more common solution between the ECMWF/GFS/UKMET with the GFS slower, and setting the pivot a bit north and west with the next system. As the next system drops south due to the upstream block, the ECMWF/UKMET outpace the GFS southward, due to the starting point of the binary interaction/pivot point being further NW, yet the subtropical moisture stream and embedded shortwave, lift at similar times to produce fairly agreeable QPF swaths into S CA to build some bit of confidence moving forward even without good mass agreement, per se. The 12z NAM is much too fast lifting the northern shortwave away and subsequently is much too far east with the developing closed low by Day 3, leading to earlier and slightly different orientation of onshore flow into S CA. Likewise, the CMC is deep and angling the moisture ashore less favorably given the other guidance. As such will favor a 00z ECMWF/UKMET and 12z GFS blend at average confidence. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina