Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 357 AM EST Sat Nov 23 2019 Valid Nov 23/0000 UTC thru Nov 26/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Cycling closed low emerging Ohio Valley, potentially phases with northern stream shortwave across Great Lakes Sat into Sun supporting associated surface low moving from the lower out of Tennessee Valley into the central Appalachians Friday night into Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/UKMET/ECMWF blend Confidence: Average 09Z update: No significant changes with the 00Z UKMET and ECMWF now available. The previous preference for a GFS/UKMET/ECMWF blend looks sufficient. Closed upper level low currently seen in GOES WV imagery over the central Plains will move eastward toward the OH Valley in the next 12-24 hours. Meanwhile, shortwave energy is quickly dropping through the northern Plains. These pieces of energy are forecast to phase into Day 2 and produce a negatively tilted trough over the Northeast U.S. with an associated area of low pressure off the Mid-Atlantic coast. A look at the most recent guidance shows the 00Z NAM a bit too aggressive with the 500 mb trough and at the surface, the low too far west / close to the coast. Meanwhile, the 12Z CMC looks a bit out of place and is too fast to lift the shortwave through New England on Day 2. The GFS, ECMWF, and UKMET all appear fairly reasonable solutions and have shown fairly good run to run consistency within the ensemble spread, so for this cycle the preferred blend will be the 00Z GFS, 12Z UKMET, and 12Z ECMWF. ...Embedded shortwaves within strong zonal northern Pacific Jet into the Northwest... ...Associated surface wave across the Northern Tier by 00z Mon... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 25.00Z; GEFS/ECENS blend thereafter Confidence: Average Fairly active northern stream energy will bring a parade of shortwaves across the northern tier of the U.S. during the short term period while a large closed low drifts well offshore the southern California coast. The large scale synoptic setup and evolution is fairly represented by the various deterministic models through about 48 hours, however, as the waves crest the Canadian Rockies there is fairly sizable spread. The 00Z GFS is too amplified as the trough digs across the Rockies on Day 3, well outside the ensemble spread and also is a bit fast compared to the rest of the deterministic timing on Day 3. Otherwise, there is some timing differences with the UKMET, particularly with the upstream shortwave coming into the Pac NW toward the end of Day 3. Given the larger than usual spread in the models, the Day 3 preference is for more use of the GEFS/ECENS means, with a general model blend for the first 48 hours of the forecast. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor