Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1230 PM EDT Thu Jun 06 2019 Valid Jun 06/1200 UTC thru Jun 10/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Confidence and Preference ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12z GFS/00z ECMWF (70%) w/12z NAM (15%) Northern Stream: + 00z UKMET (15%) Southern Stream: + 00z CMC (15%) Confidence: Average (southern stream) Slightly above average (northern stream) The models continue to support of a rather amplified northern stream pattern with a southern stream taking on a slow moving/blocky pattern over the next 2 to 3 days. This will be characterized by a rather deep northern stream trough crossing the Pacific Northwest Thursday into Friday before then lifting northeast toward central Canada this weekend, due to the enhanced ridging from the southern stream (north-west of the block). The southern stream trough/closed low over the southern High Plains will continue to advance slowly east pumping this central US ridge, with the eastern portion of the warm conveyor belt extending across the southern Mid-Atlantic into the Carolinas feeding peripherally to exiting long-wave trough in the Northeast. Eventually, this connection to the northern stream severs and ridging builds in the Northeast and the closed low stretches both north into the approaching northern stream trough across the Midwest as well as dropping internal shortwave to the Gulf Coast. Typical model biases manifest throughout the forecast period, with the GFS trending faster than the slower ECMWF and CMC with the 12z NAM a bit slower than the GFS, but also stronger internally with each shortwave. The main outlier appears to be the UKMET, while following some typical stronger but faster known negative bias, the 00z run seems to be very egregious, leading to greater influence on the surrounding environment with a stronger concentric closed low in the TN Valley by the end of the forecast period on Sunday. GEFS and ECENS solutions are fairly well agreed given a hard predictability pattern with a closed low that will have convective upscale feedback important to its longer term maintenance. A blend of the 12z GFS and the 00z ECMWF would handle this setup best, though some inclusion of the 12z NAM and CMC at lower weighting will help. In the northern stream, as alluded to before, there is a bit less model spread given the stronger baroclinic influences (cold air presence). Here, the 00z CMC is much slower and compact rolling through the northern US/southern Canadian Rockies and keeps the strong/compact inner core that delays its eastward progress. The 12z GFS/NAM have stabilized a bit around a slightly faster solution than the ECMWF/ECENS solution, but more of a typical timing/placement spread enough to blend. The UKMET is viable in the northern stream as well, but is even a bit faster than the GFS. So would include it but at a lower weighting. All in all, a 12z GFS/00z ECMWF blend would be preferred with the 12z NAM (at lower weighting) with equal weighting (to the NAM in the larger blend) to the CMC or the UKMET, base on the stream respectfully (southern-CMC and northern-UKMET). Confidence is average in the overall blend, but maybe slightly above average in the northern stream given the tighter overall solution/QPF packing. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Gallina