Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 236 PM EDT Tue Mar 12 2019 Valid Mar 12/1200 UTC thru Mar 16/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall CONUS... ~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average 19z update: The 12z UKMET/CMC both shifted well while the ECMWF remained fairly consistent, providing much better agreement with the deepening cyclone through the Plains as well continuing into the Upper Midwest/Great Lakes by Friday. The CMC is a bit weak with the upstream ridging across the northern Plains at 84hrs and the UKMET is generally weaker throughout the overall forecast period, but the track/timing looks fairly solid. This leaves the NAM as the main outlier, mainly after Thursday in the Great Lakes of an otherwise very good model agreement. The main mass differences remain in CA/Southwest on Day 3. Will favor the ECMWF more heavily given continuity, though there are limited moisture/sensible weather with any solution. ---Prior Discussion--- Current GOES-16/17 WV Mosaic depicts a very strong/compact closed low over the Lower Colorado River with well defined features, including well shaped subtropical jet and western branch of low level warm conveyor. Further northwest, a similar polar jet structure resides on the eastern side of a sharpening/digging shortwave crossing into SW OR/N CA at this time. This upstream wave will continue to dig with a strong undercutting jet through the desert southwest further amplifying (with negative tilt) the closed low leading to rapid lee cyclogenesis deepening in E CO/W KS Wed. Models are coming into solid agreement, enough to start discerning smaller scale differences. The 12z NAM is a bit north and west with the surface low track through the Plains, but is not substantially out of phase through until the cyclone reaches the Upper Midwest/Northern Great Lakes Fri. Here, the NAM is draws energy (a bit colder thermally too) southward sharper leading to some increased spread in mass fields. Similar but on the opposite side, the CMC is slow to draw the northern stream energy south across MN, leading to a slight slowing of the shearing deep closed low in the Great Lakes relative to the 12z GFS/00z ECMWF and ensemble suite. The 00z UKMET is also a bit fast ejecting into the Great Lakes as well as the northern stream energy digging faster than other guidance would support as well. This leads to a fairly confident 12z GFS/00z ECMWF blend (mainly after Thurs). This blend should also work throughout the remainder of the CONUS in the short-term. The shortwave currently over ND will slide over the ridge in the Great Lakes and through New England with lower fanfare. Similarly, a shortwave emerging from the Pacific Thursday will reach CA and start to settle into a broader trof with a potential closed decameters at 5H at 84hrs. Here a GFS/ECMWF blend will suffice, though ensembles (CMC/UKMET too) would suggest a more consolidated closed feature nearer the ECMWF solution, so weighting that direction in the blend seems prudent for CA/Southwest at the end of day 3. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina