Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 222 AM EDT Sun May 12 2019 Valid May 12/0000 UTC thru May 15/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation Including Final Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall CONUS except Pac NW... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average 07z update: The 00z ECMWF trended a bit weaker and east shift with the surface wave off the New England coast more in line with other guidance further solidifying the initial preference. Little change elsewhere keeps confidence above average in this general model blend ---Prior Discussion--- Closed low over the Plains will progress across the Midwest into the Ohio Valley Monday and into the Northern Mid-Atlantic by early Tuesday. Guidance is fairly solid in agreement until the closed becomes concentric becoming fully mature Tues into Wed over the NW Atlantic/S New England. The 12z ECMWF is very tight with the internal shortwaves allowing it to be uncharacteristically fast in coastal low development with the strongest surface response, it is supported by the CMC and a bulk of ECENS members, but just a bit odd. The 00z NAM swings an internal shortwave around the base with increased negative tilt orientation and less concentric with the closed low through this time period, leading to the surface wave being a bit further east before rotating back toward the Gulf of ME. The UKMET, like the GFS is a bit slow but still tracks well to the overall cluster. Overall, the agreement is pretty good through day 1-2 with only minor separation at day 3 to support using a general blend compromise. The closed low over N Baja California continues to come into very strong model agreement as well, the ECMWF is a bit slower to weaken/shear out the closed low across TX into the MS Valley late Tues into Wed relative to other guidance likely leading to slightly different placement/orientation to the QPF axis across TX into the Northern Gulf. Would favor the GFS/NAM/UKMET/CMC a bit more here but still not remove the ECMWF/ECENS solution from a general model blend, perhaps just slightly lower weighting toward the end of day 3. Confidence is above average through the early forecast becoming slightly above average by Day 3 mainly in Northeast. ...Upper trough/cold front approaching the Pacific Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12z UKMET/CMC/ECMWF and 18z GEFS mean blend Confidence: Average 07z update: The 00z ECMWF/UKMET/CMC all trended a bit faster in the northern stream portion of the broad trof, while still slower and broader with the wave than the sharp/fast 00z GFS and lesser so 00z NAM, it is still generally preferred over the GFS/NAM solutions. In a faster solution, less energy is dropped into the base of the larger scale trof off the CA coast, but still this is in line with initial preference just a shade weaker. As such will keep initial UKMET/CMC/ECMWF blend with the 00z GEFS mean. Confidence remains average given the above average spread and slight break from continuity. ---Prior Discussion--- A broad Pacific trof advances toward the Pacific Northwest by Tuesday. The 00z NAM and GFS both continue to trend faster away from consensus bringing in lead height-falls fairly sharply with some negative tilting to the trof by 00z Wed. While the 12z UKMET is next in line with this solution, the ECMWF/CMC both suggest a stronger closed low solution and digging jet energy around the base and enhancing the broad base of the trof that extends to central and Southern CA. Given the GFS fast bias and continuity favoring the slower solution will favor a 12z UKMET/CMC/ECMWF blend with some 18z GEFS mean to help hold continuity and dove-tail into the medium range preference (please see more in WPC PMDEPD). Broad flow, slightly above average spread provides average confidence in this preference. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Gallina