Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 309 AM EDT Sun May 24 2020 Valid May 24/0000 UTC thru May 27/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Shortwave trough crossing the Great Lakes through Sunday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average A rather compact mid to upper-level low center crossing the Midwest this evening will be advancing across the Great Lakes region on Sunday and weakening with time as it tracks over the top of a strengthening deep layer ridge over the Southeast U.S. On Monday, a weak remnant of this energy will cross through northern New England. The models are in good agreement with this system, and so a general model blend will be preferred. Deep upper trough crossing the Intermountain West to the Plains Lead shortwaves crossing the southern Plains Sunday/Monday Closed low formation over the southern Plains by Tuesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...upper trough evolution 00Z NAM/UKMET/ECMWF blend...surface low evolution Confidence: Average The latest guidance shows very good agreement in bringing a new large scale upper trough and associated closed low in across the Intermountain West through the weekend. By Monday, the models support this deep trough edging toward the Plains with one closed low center exiting the northern Rockies and crossing the northern High Plains. Meanwhile, a second closed low will be attempting to focus over the central Rockies, and by Tuesday the guidance is in reasonably good agreement on the idea of a new closed low becoming well-defined over the southern Plains. Leading up to this closed low evolution over the southern Plains, there will be a pair of shortwave troughs, one on Sunday and one on Monday, that will round the base of the larger scale trough and lift northeast across the southern Plains. The first shortwave is expected to evolve out of the MCS activity currently impacting areas south-central TX and the middle Rio Grande Valley. The second and more dominant shortwave is currently showing up very distinctly across the Southwest U.S. and northwest Mexico in GOES-WV satellite imagery, and is moving steadily off to the east. The 00Z NAM and 00Z GFS are just slightly stronger than the 00Z non-NCEP models with the first shortwave, but the mass fields are really quite modest. This energy will lift northeast through Sunday night toward the lower MS Valley as the second upstream shortwave trough arrives and ultimately fosters the upper low development over the southern Plains by Tuesday. With the second shortwave, the NAM and GFS are also a tad stronger than the non-NCEP models, with the GFS also being a tad on the faster side of the guidance. However, by the end of the period, the guidance does cluster better now with the placement of the upper low over central TX, with only the NAM appearing to be perhaps a little too slow with its eastward ejection of it. The 00Z GEFS mean also supports this placement, with the former 12Z ECENS mean just a tad off to the east. There is better agreement too with the surface low center evolution, which now is converging on the idea of a stronger low over southeast KS early Tuesday, and then a more modest wave over east TX by early Wednesday. The GFS looks too weak now with its solution over KS, with the CMC probably too far to the west, but the NAM/ECMWF/UKMET solutions are better clustered over southeast KS, and these solutions also all favor the modest wave over east Texas. By the end of the period, the GFS still looks like it is too wrapped up and too far west with its TX low center, and the CMC too far north with a wave over eastern OK. Based on the latest model trends and clustering, a general model blend will be preferred with the broader upper trough, shortwaves and closed low evolution. However, with the surface waves, a blend of the NAM, UKMET and ECMWF will be preferred. Mid-level trough impacting Florida early in the week Weak surface low over east-central Gulf of Mexico ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM/GFS/ECMWF blend...for the mid-level trough 00Z NAM and 12Z/00Z ECMWF blend...for the Gulf low Confidence: Average As a strong subtropical ridge builds over the Southeast and the Mid-Atlantic region going into the beginning of the week, there will be a mid-level trough axis lifting north from the Yucatan Peninsula and western Caribbean Sea to the southern Gulf of Mexico. This energy is expected to elongate and cross areas of southern Florida by late Monday and into Tuesday. There is also growing support for a weak area of low pressure to form along an inverted surface trough as well, with the 00Z NAM, 12Z ECMWF and a large number of European and Canadian ensemble members suggesting surface low development. The 00Z HREF model suite also supports this as well. With respect to the mid-level trough, the 00Z UKMET again remains more suppressed with it and this is a result of the UKMET being stronger with its subtropical ridge to the north over the Southeast U.S. The 00Z CMC is also somewhat suppressed too, but not to the same extent. The 00Z ECMWF came in still farther north with its mid-level trough evolution, but it did trend a tad farther south with its Gulf low center, and also it has a much sharper eastward extending trough across the FL Peninsula along with evidence of a second low center (possibly from convective feedback) near the east coast of FL from 48 to 72 hours. The UKMET also eventually suggests a low center off the east coast of FL, except it is farther south. The mass field preferences are a little complicated, but a blend of the NAM, GFS and ECMWF will be preferred for the mid-level trough evolution, but for the weak surface low feature over the Gulf of Mexico, a blend of the 00Z NAM and the last two runs of the ECMWF (00Z/12Z) will be preferred which would help to mitigate the new ECMWF possibly being a bit too aggressive with its surface trough over FL along with its low center near the east coast of FL. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison