Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1215 PM EDT Thu May 30 2019 Valid May 30/1200 UTC thru Jun 03/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model Blend Exception: 06z GEFS/00z ECENS Mean blend in Great Lakes/Northeast after 02.00z Confidence: Slightly above average Models continue to be in fairly solid agreement especially across the Western US with the closed low consolidating today as it slides into a relatively stationary position in S California/S Great Basin for the remainder of the forecast period. Eastern regions will see more turbulent weather given large scale vortex anchored over NE Ontario and Quebec for the forecast period, with other systems (some quite strong) along the periphery moving through the Upper Great Lakes, eastern Midwest and Mid-Atlantic and New England, leading to the greatest model spread. The persistent closed low/shortwave across Iowa will slide east shedding shortwave energy today into the confluent flow across the Mid-Atlantic spurring a weak coastal development south of Long Island by early Fri. Guidance here shows typical bias but it is minor to continue supporting general model blend. The main core remains upstream in Ohio and is stubborn to shear and slides through the southern Mid-Atlantic by Sat morning; here spurring another more significant surface wave. Unlike the prior system, the spread becomes larger with the CMC a bit stronger and uncharacteristically fast. So a Non-CMC blend is supported with this feature at slightly above average confidence. By Saturday, the larger vortex in Quebec will be joined by a smaller but still very strong compact closed low driven by abnormally cold dropping as far south as the northern Great Lakes. Differences in the magnitude of binary interaction between the pair of closed seems to be driving the major model spread. The initially colder CMC and UKMET both favor the new shortwave dropping south over the initial centroid, this leads to a stronger, deeper solution of the surface wave through the Great Lakes through the late weekend. There is a trend toward this stronger/deeper solution; both these models go above and beyond the average of the ensemble suite, particularly the UKMET which is fast/east of the bulk of solutions. However, the 12z GFS, following its 06z run was also more compact slower and deeper, not to the level of the CMC or UKMET but on par with the NAM. Interestingly, the ECMWF seems to have swapped traditional place with the GFS, as the is ECMWF weaker and faster progressing through the Great Lakes by 03.00z Monday. The ECENS solutions and GEFS members generally are betwixt their operational solutions and show minor spread with the suite to suggest this is a good pairing and in line in timing with the deeper solutions of the NAM and CMC. While the mass fields are jostled up, the overall QPF looks fairly agreeable with the prior discussed minor timing differences, particularly the fast ECMWF. As such would favor the middle-ground hedging to the GEFS/ECENS (even the SREF mean looks reasonable) for mass fields over any particular deterministic run so far, though the NAM may be the best single representative at this point and may include more deterministic with further model agreement with the 12z runs of the ECMWF/UKMET/CMC. QPF is likely a general model blend though finding a more central timing placement of the QPF maxim through the Great Lakes and Northeast. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Gallina