Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1235 PM EDT Fri Nov 02 2018 Valid Nov 02/1200 UTC thru Nov 06/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS/ECMWF/UKMET Confidence: Slightly Above Average Exiting shortwave along East Coast today, with amplifying MO River Valley shortwave and surface low along the East Coast into Canada Sat into Sunday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average confidence Currently, elongating/stretching shortwave/atmospheric river across east-coast will continue to shift east with good model agreement, but as the shortwave across the Lower MO river valley shifts east and strong jet streak descends and rounds the base of the mean trof...the wave will buckle and support enhancement tonight through Sat into the Northeast with deepening surface cyclone through the Mid-Atlantic, into a strong/deep cyclone through the St. Lawrence Seaway, the model agreement is strong enough (typical biases - GFS/NAM fast, ECMWF/CMC a bit slower) in the mass fields to support an above average confidence in general model blend. Pacific Northwest trof amplifying over Central Plains shifting into Great Lakes and interaction/spacing with fast/strong jet entering the Pacific Northwest Sun and digging in Central Plains bu 00z Tues and the effects felt into the Southeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET through 04/12z shifting to 12z GFS/NAM and 00z CMC blend Confidence: Slightly above average thru 04/12z Slightly below average thereafter The greater uncertainty occurs with the next shortwave entering the mean global trof over the Central US. This wave has a reduced amplification overall, but there remains modest spread. The 06z GFS and GEFS were generally weaker and more importantly a bit north within the spread... which leads to reduced Gulf moisture flux/mass convergence for convection/QPF. While the NAM is a bit faster, the UKMET is very slow perhaps a bit too much even lagging the ECMWF/CMC...but still remains quite representative and viable overall. The 12z GFS slowed and deepened in respect to the NAM/06z GFS but remains significantly less deep/sharp as the ECMWF especially in the 3-250mb range with the timing/strength of the jet. While this may not be a large model variance for this wave, and better agreement overall; it is clear the spacing with the approaching shortwave/mean large scale jet core entering the West Coast, is a big difference. So will include the 12z GFS with the NAM and CMC, The 00z ECMWF having a deeper/sharper wave breaks from ensemble/other deterministic general consensus with the wave out of the southern stream becoming confluent with Tropical Atlantic/Caribbean stream, as the ECWMF height falls draw this trof/confluence boundary north and west into the Southeast, where consensus/general meteorological concepts suggest this is a bit too aggressive and should favor an axis through the coastal plain/coast or even along the western boundary of the Gulf Stream. The other affect of the more amplified solution is to support a faster/stronger jet with the next wave allowing for a deep negative tilt shortwave to tighten around 00z on the 6th. While the pattern of a more amplified system is favored, the degree to which the 00z ECMWF goes should be scaled back. The 12z GFS having reduced the spacing between waves allows for this deeper/sharper amplification. The UKMET having been slow with the initial wave is too close in spacing and drives the next wave faster forward than much of the remaining suite (with exception of the 12z NAM), leading to a deep but much broader trof that is generally front loaded looking at the vorticity fields. So here a 12z GFS/NAM and 00z CMC seem to be be a good compromise...Confidence is slightly to below average. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina