Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 128 AM EST Tue Jan 14 2020 Valid Jan 14/0000 UTC thru Jan 17/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Large Scale Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00z GFS/ECMWF blend Note: CMC ok for mass fields Confidence: Slightly above average 07z update: The 00z UKMET trended even faster across the Great Lakes, and while it did shift a bit north, it continues to be a stronger/south outlier to the suite. Additionally, typical known negative bias manifests along the S CA coast at the end of D3. This matches (a tad stronger) than the 00z NAM and while it tracks, timing-wise well with the other guidance, this stronger solution is a tad too aggressive for day 3 with the two most aggressive models. The 12z ECMWF trended a bit slower across the Pacific northwest trending toward the GFS/NAM and CMC with this system providing additional growing confidence with the closed low; unlike the UKMET/NAM it is more sensible across the base of the trof crossing S CA and so a GFS/CMC/ECMWF blend is supported there. In the Northeast, the CMC is a bit further south, but did pick up pace to the overall suite. Still will favor a GFS/ECMWF blend for this system, the CMC and NAM still seem to have some weak support and remain viable within a blend if desired to account for the mild uncertainty. ---Prior Discussion--- A large scale consensus started last evening in handling the remains of the Arctic vortex hub across BC/Alberta, and now the last stragglers have come into line with the ECMWF/ECENS solutions wrapping the energy back west into the developing closed low/broad cyclone near Vancouver Island. The energy that does shear downstream in the wake of the last fast moving Pacific shortwave that is currently entering the Pacific Northwest (and remains in solid model agreement through its trek through the Northern Plains into the Great Lakes Wed/Thursday) leads to evolutionary differences in timing/latitude for the system across the Lower Great Lakes into the Northeast by Thursday. Here, the 00z NAM has trended more favorably, yet still is quite strong with both the leading shortwave as well as the sheared energy across the Great Lakes, supporting very deep coastal low development and greater overall amplitude of the wave by 00z Fri and is within the realm/bulk of ensemble solutions if just a tad too deep. The 12z UKMET is a bit too fast with the Pacific stream wave and therefore evolves a bit further south across New England into coastal waters to be supported here. The 12z CMC is generally slow about 3-6hrs relative to the ECMWF/GFS but at least shows a very similar evolution/interaction through the depth of the developing wave to keep at lower weighting in the preference. Otherwise, an ECMWF/GFS blend is supported at slightly above average confidence (with some inclusion of the CMC/NAM to account for some lower probabilities). As for the west developing/deep closed low and high amplitude trof by Wed/Thurs. The ECMWF continues to be very strong but very uncharacteristically fast to deepen/occlude. While, this has been a very consistent signal it is a bit concerning given the GFS is equally slow, almost if they swapped traditional model differences (roles). The UKMET is more like the ECMWF and the CMC/NAM are more GFS like. The larger difference manifest in the shortwave that carves out the base of the high-amplitude trof entering the CA coast late Thursday. Here the NAM looks to have typical end of cycle, over-amplification negative bias. So generally, an ECMWF/GFS blend with lower weight inclusion of the UKMET/CMC is preferred at slightly above average confidence as well. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina