Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1240 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: Blend of the 12Z ECMWF/ECENS mean and 18Z GEFS mean 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 a tad stronger than the 12Z non-NCEP models with the first shortwave, which is likely a reflection of their 00Z sampling/cycling of the ongoing convection. 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 00Z NAM and 00Z 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. The 12Z UKMET is perhaps a bit too weak with the second shortwave trough which results ultimately in a somewhat weaker upper low evolution. The 12Z CMC by the end of the period is also seen as being a bit too far north with its upper low. Meanwhile, the 00Z NAM appears to be a tad too slow in ejecting the deeper layer trough and closed low off to the east by the end of the period. The 12Z ECMWF, 12Z ECENS mean, and 18Z GEFS mean are well clustered with the upper low Tuesday through early Wednesday, and also with their corresponding surface wave reflections for which the NAM/CMC camp suggests stronger wave activity lifting north across KS, and the GFS/UKMET camp with low pressure more concentrated over areas of southwest OK and northwest to north-central TX. A more elongated axis of low pressure is likely to evolve with multiple waves that lift across central/eastern TX and northward up across eastern OK and eastern KS late Tuesday through early Wednesday as this is likely where a slow-moving or quasi-stationary front should be positioned. Will prefer a blend of the ECMWF, ECENS mean and GEFS mean at this point with the shortwaves and closed low evolution. Mid-level trough impacting Florida early in the week Weak surface low over east-central Gulf of Mexico ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend...for the mid-level trough 00Z NAM/12Z ECMWF blend...for the Gulf surface 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 12Z 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 model preference will be toward a non-UKMET blend with the details of the mid-level trough given decent model clustering seen otherwise with this, but with the weak surface low feature over the Gulf of Mexico, a blend of the 00Z NAM and 12Z ECMWF will be preferred. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison