Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 241 AM EDT Tue May 22 2018 Valid May 22/0000 UTC thru May 25/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z model evaluation...including preferences and confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Trough digging across the Northeast by Tuesday/Wednesday... ...Surface low crossing the OH Valley and Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The guidance generally depicts an amplification of a northern stream shortwave trough across the Northeast through Tuesday and Wednesday as a surface wave ejects across the OH Valley and interior of the Northeast. There is good agreement seen out of the models and so a general model blend will be preferred. ...Large scale trough/closed low impacting the West... ...Energy crossing the northern High Plains by Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend Confidence: Average The models are in excellent agreement in digging height falls across the West through Tuesday which includes a well-defined closed low that digs in across the Southwest. On Wednesday, this closed low feature will lift off to the northeast, and the energy should open up into a progressive trough by Thursday that will be ejecting up across the northern High Plains. The 00Z UKMET by the end of the period appears to be a little too progressive in taking its energy across the Dakotas. The remaining guidance is relatively well clustered with some modest timing and depth differences. Will suggest a non-UKMET blend at this point. ...Mid level trough/closed low lifting up across the Southeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The guidance is in very good mass field agreement with this system, so a general model blend will be preferred. ...Shortwave energy/vorts lifting across the Plains Tuesday and Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average Multiple shortwave impulses are expected to lift northeast out of the base of the Western U.S. trough and across the Plains on Tuesday and Wednesday, and there appears to be better model clustering at this point with the overall details. The 00Z GFS does exhibit a little bit of convective feedback from the outset over southeast NM with its ejecting energy, but then quickly comes into alignment with the remaining models across the Plains through the period. Will prefer a general model blend as a result. ...Upper trough/closed low offshore the West Coast by Wednesday and Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend Confidence: Slightly above average The models drop another upper trough and associated closed low feature south down off the West Coast by Wednesday and Thursday. The 00Z UKMET is a bit weaker than the remaining models with its closed low offshore CA by the end of the period and is also a bit farther south. The remaining guidance is rather well clustered on a bit stronger solution that is a little farther north. Will suggest a non-UKMET blend at this point. ...Surface low development over the Gulf of Mexico by Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z ECMWF Confidence: Average The latest deterministic guidance and ensemble plots generally favor the idea of a relatively broad low to mid level low center evolving north of Yucatan Peninsula by Friday that will be lifting north toward the central Gulf of Mexico. The 00Z NAM is by far the faster solution with this as it has a low approaching the north-central Gulf Coast at the end of the period. The 00Z UKMET has come around to the idea of a more developed low center, but it along with the 00Z CMC are very slow and actually have the system down near the Yucatan Peninsula at the end of the period. The 00Z ECMWF splits the difference and remains consistent with a low that is over the central Gulf of Mexico. Finally, the 00Z GFS again has very little in the way of a low at least through this period and instead suggests an open trough axis moving up toward the southern Gulf of Mexico. The latest ensemble data is rather strongly in favor of a developing low led especially by the European and Canadian ensemble members, but also including a number of GEFS members which suggest the GFS is too benign with its evolution of this system. The preference will be toward the 00Z ECMWF given the degree of 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