Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1225 AM EDT Mon May 25 2020 Valid May 25/0000 UTC thru May 28/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Weakening shortwave crossing northern New England on Monday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average A mid-level trough currently weakening over the Great Lakes region will dampen further on Monday while shearing across northern New England. The models are in good agreement with the details of this, so a general model blend will be preferred. Shortwave over the northern Plains through Monday Reloading northern stream trough over northern Plains by Wednesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM/GFS and 12Z ECMWF Confidence: Slightly above average A closed low initially over Wyoming and eastern Montana is forecast to evolve into an open wave as it reaches the western Dakotas by Monday afternoon. By Tuesday this disturbance should become absorbed by the westerlies across southern Canada. The guidance is in good agreement with the details of this exiting system. However, by later Tuesday and into Wednesday, the models support amplification of a new northern stream trough over southern Canada and the northern Plains. This will drive surface low pressure across southern Canada with a trailing cold front that will be crossing the northern Plains. The models overall are fairly well clustered with the height fall evolution of this next trough, although the 12Z UKMET becomes a bit of a progressive outlier by late Wednesday, and the 12Z CMC is perhaps just a tad too slow. The 00Z NAM/GFS and 12Z ECMWF are well clustered in between toward the end of the period, and based on this, a blend of these solutions will be preferred. Synoptic scale trough over the West evolving into closed low over southern Plains ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS and 12Z ECMWF Confidence: Slightly above average A synoptic scale upper trough initially over the Intermountain West will drop east-southeast over the central and southern Plains over the next couple of days, with a cut-off upper low expected to set up over far northern TX by late Tuesday. This upper low should then drift very slowly eastward through northeast Texas by early Thursday. Model mass field spread is minimal through early Tuesday, but by late Tuesday through the end of the period, the 12Z UKMET ends up on the south side of the guidance with the position of the upper low. Toward the end of the period, the 12Z CMC also looks like it may be a tad too slow, as the 18Z GEFS mean and 12Z ECENS mean support the 00Z NAM/GFS and 12Z ECMWF with an upper low that is over northeast TX. At the surface, multiple waves of low pressure will be lifting north along a front advancing east across the Plains. Generally the better model clustering and ensemble support resides with the 00Z GFS and 12Z ECMWF. So, based on the latest trends and clustering of solutions, a blend of the 00Z GFS and 12Z ECMWF will be preferred for the mass field evolution of the upper trough and surface waves. Mid-level trough and weak surface low impacting Florida ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM/GFS and 12Z ECMWF Confidence: Moderate An upper level ridge will be building across the Southeast U.S. early this week and gradually out across the western Atlantic by midweek. South of the upper ridge will be a low to mid-level trough axis which is expected to lift northward through the eastern Gulf of Mexico and the FL Peninsula going through Tuesday. By Wednesday, this energy will be advancing north into the Southeast U.S. within deep layer southerly flow situated between the deep upper low over northeast TX and the building ridge over the western Atlantic. Multiple waves of low pressure, possibly convectively induced, are expected to evolve with this system with one low lifting north across the eastern Gulf of Mexico, and another forming near the east coast of FL. Generally the guidance is more subtle with the wave over the eastern Gulf of Mexico versus the wave along the FL east coast, as the 00Z NAM/GFS and 12Z ECMWF all have rather well-defined lows in the vicinity of Melbourne, FL by 12Z Tuesday. The 12Z CMC is more ill-defined with it, but the 12Z UKMET eventually forms a rather well-defined low by late Tuesday in the same area. The main takeaway with the 12Z UKMET is that it is again slow to lift the low to mid-level trough northward and thus is slower with its surface waves. By the end of the period, all of the models show a surface wave attempting to lift through the Southeast U.S. as the supporting mid-level trough lifts north. The 12Z CMC and 12Z UKMET are the most divergent solutions relative to the model consensus, with the better model clustering and ensemble support favoring a blend of the 00Z NAM/GFS and 12Z ECMWF, and thus this will be the preference at this time. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison