Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1219 AM EDT Sat May 23 2020 Valid May 23/0000 UTC thru May 26/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Cut-Off Low impacting the OH Valley and northern Mid-Atlantic... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models are in very good agreement with the details of the cut-off upper low currently over the upper OH Valley which will advance east across the northern Mid-Atlantic region on Saturday and then move offshore. A general model blend will be preferred with this system. ...Deep upper trough/closed low reloading over the Western U.S... ...Ejecting out over the Plains by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 48 hours 18Z GEFS mean/12Z ECENS mean blend...after 48 hours Confidence: Average...becoming below average after 48 hours The latest guidance shows very good agreement in bringing a new large scale upper trough and associated closed low in across the Intermountain West this weekend. By early next Monday, the consensus of guidance supports a deep trough edging toward the Plains with one closed low center exiting the northern Rockies and crossing the northern High Plains by then. Meanwhile, a second closed low will be attempting to focus over the central Rockies by then, and by Tuesday, the guidance is in reasonably good agreement on the idea of this closed low becoming better defined out across the southern High Plains. The models generally show good agreement with their mass fields through 48 hours, but thereafter the 12Z UKMET is seen as focusing more of its closed low energy farther north over the central Plains versus the southern Plains. The 00Z NAM/GFS and remaining 12Z non-NCEP models all have an upper low that is over in vicinity of the TX Panhandle by Tuesday. This will also result in a corresponding surface low, and with this feature there is greater spread. The 12Z CMC has a weaker and northerly tracking low center up over northern MO at the end of the period versus the 00Z NAM which is stronger and has the low down over central OK. The 00Z GFS and 12Z UKMET have the low near the southeast KS/northeast OK border, and the 12Z ECMWF has no surface low at all. The 18Z GEFS mean and 12Z ECENS mean both have a well-defined front across the Plains and stretching up toward the upper Midwest by the end of the period, but do not necessarily suggest a well-defined low at this point, and upon inspection of individual members, there is significant spread with the details of surface wave activity along the front over the central and southern Plains region from Monday into Tuesday. A general model blend should generally suffice with this entire mass field evolution through 48 hours, but thereafter as the deep trough/closed low ejects out across the Plains, a blend of the latest GEFS mean and ECENS mean will be preferred given the large spread in the details of surface low pressure. Fortunately, there is reasonably good agreement with the details of the energy aloft, outside the aforementioned UKMET solution. ...Shortwave/closed low crossing the Midwest through Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend Confidence: Above average The latest GOES-WV satellite imagery shows a very well-defined closed low over far southeast NE which will be advancing northeast across the upper Midwest through Saturday and then gradually weakening over the Great Lakes region on Sunday as it attempts to crest the deep layer ridge forming and nosing northward by then over the OH/TN Valleys and Southeast. Overall, the guidance is in good agreement with this system, but the 12Z UKMET after about 36 hours hangs onto a stronger trough that exits the Great Lakes and moves into portions of northern New England by early Monday. Given good clustering in the guidance otherwise, a non-UKMET blend will be preferred. ...Shortwave lifting northeast across the southern Plains Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 18Z GEFS mean/12Z ECENS mean blend Confidence: Slightly below average As the deep trough and associated closed low evolves across the West this weekend and slowly encroaches on the High Plains, there will be a shortwave trough rounding the base of it and lifting northeast across the southern Plains on Sunday. The 00Z NAM/GFS solutions are bit stronger with the energy lifting northeast and even suggest the potential for a more discreet mid-level low center developing over central TX by Sunday night. The non-NCEP solutions by comparison are all a tad weaker. A blend of the ensemble means will be preferred for the time being as a compromise, but which also do have reasonably good agreement with each other in being not quite as strong as the NAM/GFS camp. Confidence is a tad limited. ...Mid-level trough impacting southern FL Monday and Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z NAM/GFS and 12Z ECMWF Confidence: Below average As a strong subtropical ridge builds over the Southeast and the Mid-Atlantic region Sunday and Monday, there will be a mid-level trough axis lifting north from near the Yucatan Peninsula and western Caribbean Sea into the southern Gulf of Mexico. This energy is expected to elongate and cross areas of southern FL by late Monday and through Tuesday. The 00Z NAM/GFS and 12Z ECMWF are all farther north with the trough axis versus the 12Z CMC and 12Z UKMET. There has been a multi-model trend to focus a stronger mid-level trough a bit farther north over the southeast Gulf of Mexico and southern FL for Monday and Tuesday, with the NAM/GFS and ECMWF all trending in that direction, so will favor a blend of those solutions at this time with the mass field details. Confidence is limited though for the time being in the details of this evolution since there is still meaningful deterministic model spread. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Orrison