Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 120 AM EST Sun Mar 03 2019 Valid Mar 03/0000 UTC thru Mar 06/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation Including Preference and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Phasing short waves and resulting surface low tracking from the Mid Atlantic to Newfoundland... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average 07z update: The 00z ECMWF adjusted toward the growing tight consensus to support a general model blend throughout the forecast period for this system. ---Prior Discussion--- Flattening shortwave crossing out of the Central Rockies will support surface development in the Mid-South that will shift across the Carolinas and deepen near the 40N70W benchmark. Guidance has come into solid agreement with the phasing/timing of this feature, with one exception. The 12z ECMWF continues to be stronger and cyclonically track left of the consensus track toward SE MA early Monday, which also affects the QPF axis. It remains slightly out of place, but with the CMC a bit slow and the UKMET a bit east...its incorporation seems perfectly fine across the south and southeast, but not so much across the Northeast. The 00z NAM/GFS both continue to be fairly consistent and agreeable to this blend. As such confidence is increasing to slightly above average in a Non-ECMWF blend after 04/06z. ...Closed mid-level low near WA coast Monday... ...Trough approaching CA Coast Tuesday.... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Exception: 00z ECMWF/UKMET/CMC blend in Pacific NW. Confidence: Average 07z update: The southern stream system remains well timed, and given it has the QPF/sensible wx impact a general model blend can be supported. As for the northern stream binary interaction, the ECMWF slowed and was accompanied in good positioning/timing with the UKMET/CMC. The GFS is slow to this timing, but shows an eventual similar process providing confidence toward shifting preference toward the ECMWF/UKMET/CMC for this area at average confidence. ---Prior Discussion--- At the tail end of the elongated trof across the Northern Plains into the Northwest, flow weakens and supports a consolidation of vorticity energy over the Pacific Northwest and by early Tuesday there is fairly solid consensus of a concentric closed low. Upstream near the AK panhandle, a secondary tail end trof is closing into a compact system as well. Model spread significantly increases on the magnitude/timing of a binary interaction (or lack thereof) of these two features. The 00z NAM does not interact these features with only a slight northward drift of the NW system. The 00z GFS, relative to prior GFS runs, still favors the northern stream shortwave in the binary interaction, but has trended toward greater distance/angle of rotation. The 12z UKMET/CMC both show a more even strength and tight rotation to each, even greater than the GFS. The 12z ECMWF is a clear outlier, showing a faster/southward acceleration of the northern stream shortwave but rotating at a well distant angle of rotation standing out relative to the ensemble suite, including a bulk of the ECMWF members. Low levels are generally dry and low impact on sensible weather fields is fairly minimal overall, however, there is some effect to an approaching central Pacific shortwave feature...and only minimally by Wed. The 12z ECMWF digging the trof out of the Pacific Northwest increases the steering flow gradient allowing for the southern stream wave to shift faster within the overall suite of guidance, even compared to the UKMET/NAM. The GFS having trended a bit faster with the binary interaction has increased the southern stream wave nearly matching the other guidance. A such a general model blend can be supported (mass and QPF) for the southern stream trough approaching CA at slightly above average confidence, but the 12z ECMWF cannot be included in the mass field blend as it clearly is an outlier...and would suggest incorporating the ECENS mean as an alternate for the Pacific Northwest. Confidence is average given multiple streams, binary interactions that are highly contingent on timing/precise strength of each feature). Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina