Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 241 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: Non-CMC blend 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 00Z CMC late in the period edges toward the slower and deeper side of the guidance with the trough. Will prefer a non-CMC blend at this point, and this will also act as a compromise with the surface low evolution to resolve some spatial spread seen with the wave activity at the end of the period over south-central Canada. Synoptic scale trough over the West evolving into closed low over southern Plains ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS/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 00Z UKMET ends up on the south side of the guidance with the position of the upper low. The 00Z CMC is actually a tad to the north, with the 00Z NAM/GFS/ECMWF solutions clustered in between but well supported by the 00Z GEFS mean and yesterday's 12Z ECENS mean. 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 GFS and ECMWF. So, based on the latest trends and clustering of solutions, a blend of these solutions will be preferred at the surface and aloft with the mass fields. Mid-level trough and weak surface lows impacting Florida ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM/GFS/ECMWF Confidence: Average 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/ECMWF solutions all suggesting a relatively well-defined low in the vicinity of Melbourne, FL by 12Z Tuesday. The 00Z CMC and 00Z UKMET suggest the wave over the eastern Gulf of Mexico will be more defined by comparison. The 00Z UKMET still may be a tad too suppressed with its mid-level trough and associated wave activity, but the UKMET did trend farther north this cycle and toward the majority consensus. Will continue to favor a blend of the NAM, GFS and ECMWF for the time being given overall better ensemble support. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison