Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1233 PM EDT Mon May 28 2018 Valid May 28/1200 UTC thru Jun 01/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z model evaluation...including preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Subtropical Storm Alberto... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: See latest NHC forecast Nearest Guidance: Blend of the 12Z NAM and 00Z ECMWF The latest model guidance is relatively well clustered on the track of Subtropical Storm Alberto as the system is expected to make landfall early this evening across the western Florida Panhandle and lift steadily north over the next few days across the Tennessee and Ohio Valleys. By 72 hours, the guidance is rather well clustered on Alberto reaching up over northern lower MI. The 00Z CMC and 12Z GFS both begin the lag the NHC track forecast by 24 hours which carries over through the period. The 00Z UKMET is seen as being just a tad left of the NHC track from about 48 hours onward. Meanwhile, the NHC track is rather well clustered with the 12Z NAM and 00Z ECMWF, and a blend of these solutions most closely reflects the NHC track. ...Upper trough/cold front crossing the Northeast by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in very good agreement with the mass field details of this system, and thus a general model blend will be preferred. ...Upper low/trough ejecting out of the West through Tuesday... ...Reaching the northern Plains/upper Midwest Wednesday... ...Consolidating low pressure over northern Plains... ...Shortwave crossing the central Plains/lower Missouri Valley... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS and 00Z ECMWF Confidence: Average The guidance continues to show excellent agreement with the upper low as it begins to emerge from the Rockies today through Tuesday and ejecting out across the northern Plains and upper Midwest region by later Tuesday through Wednesday. This will allow surface low pressure developing in the lee of Rockies to consolidate over the northern Plains and gradually shift east. The 12Z NAM and 00Z CMC both are a little strong aloft with their height falls ejecting out across the High Plains through early Tuesday, and by Wednesday the NAM also becomes a little more progressive than the model consensus. As the energy approaches the upper Midwest, the 00Z UKMET seems to place a little less emphasis on this energy and more on the phasing of this system with the track of Subtropical Storm Alberto over the Great Lakes region. Better model clustering and ensemble support with this system is more reflected by the 12Z GFS and 00Z ECMWF which also seem to have a bit more reasonable handling of their surface wave features crossing the Dakotas. The GFS and ECMWF also are better reflective of the model consensus with a separate shortwave feature crossing the central Plains and lower MO Valley. Will support a GFS/ECMWF blend as a result. ...Upper trough moving into the Pacific Northwest on Tuesday... ...Longwave trough moving into the West by Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z NAM/12Z GFS and 00Z ECMWF Confidence: Slightly above average The models bring an initial upper shortwave trough into the Pacific Northwest on Tuesday for which the 00Z CMC is a little slower and deeper than the model consensus with this. Thereafter, the guidance agrees in the evolution of a larger scale longwave trough crossing the West Coast and spreading into the Intermountain West by Thursday. The 00Z CMC and 00Z UKMET were both a little sharper than the 12Z NAM/12Z GFS and 00Z ECMWF with the details of the longwave trough by Thursday. Will suggest a blend of the NAM/GFS and ECMWF at this time which also has a bit better ensemble agreement. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison