Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 155 PM EST Fri Feb 01 2019 Valid Feb 01/1200 UTC thru Feb 05/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...West Coast 12Z NAM/GFS blend...Plains/Midwest 12Z GFS/UKMET/ECMWF blend...Southeast Coast Confidence: Average The start of the short range period shows a broad trough over the northeastern quadrant of the U.S. while ridging generally prevails across the western U.S. with an active southern stream jet and weakening closed low over southern AZ. Mid-level heights will rise across the eastern third of the nation while a series of upper troughs/closed lows cause heights to fall along and west of the Rockies through Sunday, and then farther east with lead energy ejecting out across the Plains and Midwest through Monday. Meanwhile, the aforementioned southern stream energy over southern AZ will advance east across the southern U.S. and approach the Southeast on Sunday. This energy will lead to cyclogenesis offshore the Southeast coastline by Sunday night. Model agreement is reasonably strong across the CONUS through about 48 hours, which includes the details of the strong upper trough/closed low coming into California tonight and Saturday which then opens up into a more progressive trough as it crosses the Intermountain West through Sunday. By later Sunday and into Monday as the energy begins to eject out across the Plains, the NAM/GFS solutions begin to edge faster than the UKMET/CMC and ECMWF. Although, there is a bit better clustering with this cycle as the non-NCEP models did tend to trend a little more progressive. These differences translate down to the surface with the evolution of surface low pressure that develops over the central Plains and lifts northeast toward the Great Lakes region by late Monday. The latest ensemble means, as per the 12Z GEFS mean and 00Z ECENS mean, strongly favor the more progressive NAM/GFS camp and suggest the non-NCEP guidance is a bit too slow. Thus, the preference will be toward the progressive camp. By Monday, there will be consolidating upper troughs/closed lows offshore the West Coast which will yield a very strong larger scale trough and closed low that will begin to edge inland across Oregon and central/northern California by Monday evening. The latest UKMET and CMC have trended a little slower, and have come into stronger agreement with the generally well clustered NAM/GFS and ECMWF camp. Thus, will favor a general model blend now with the mass field evolution of the height falls along and offshore of the West Coast. The southern stream compact closed low currently over southern Arizona is expected to open up and track east into the southern Plains Saturday morning and into the Southeast on Sunday. Out ahead of this system, a less organized shortwave is evident over the western Gulf of Mexico. As these upper level features track east over a coastal front forecast to set up along the Southeast Coast, cyclogenesis should occur. There is better support for a defined surface low in the latest ensemble guidance, but deterministic model agreement is poor by early Monday with the evolution of low pressure. The NAM and CMC are slower to push low pressure out to sea, and tend to keep the low tucked in a bit closer to the southern Mid-Atlantic coast. The GFS and UKMET are faster with the wave moving away from the Southeast coastline, and the latest ECMWF has trended in this direction as well. The ensemble low plots of the GEFS and even a majority of the Canadian members favor a more offshore/progressive solution, whereas the ECENS members tend to favor some potential for a slower evolution. Given the faster progression of the upstream shortwave trough crossing the Plains and broader Mississippi Valley region on Monday, the energy along the Southeast coast should tend to be more progressive and likely close to that of the latest GFS, UKMET and ECMWF consensus. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison