Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1243 AM EDT Wed May 23 2018 Valid May 23/0000 UTC thru May 26/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Trough digging across the Northeast through Wednesday... ...Surface low crossing the Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The guidance depicts an amplification of a northern stream trough across the Northeast through Wednesday as a surface wave ejects across the interior of the Northeast along a front settling southeast across the region. 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... ...Arriving across the Upper Midwest Friday and Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend Confidence: Average The models take the closed low feature over the Intermountain West and advance it off to the northeast on Wednesday, and the energy should eject up over the northern High Plains on Thursday. By Friday and Saturday, the closed low should weaken into a progressive trough axis that will cross the Upper Midwest. The 12Z UKMET by the end of the period appears to be a little too progressive in taking its energy across the Upper Midwest. 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 currently over 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. ...Upper trough/closed low offshore the West Coast by Wednesday and Thursday... ...Closed low moving inland across CA on Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models drop another upper trough and associated closed low feature south down off the West Coast by Wednesday and Thursday, and then eject this system eastward across CA on Friday. The guidance is rather well clustered on the progression of this system, so a general model blend will be preferred. ...Weakening shortwave/front approaching the Pacific Northwest late Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-CMC blend Confidence: Above average The models bring a weakening shortwave trough and associated cold front in toward British Columbia and the Pacific Northwest by late Friday. The 12Z CMC is a bit of a slower and weaker outlier with the shortwave and is slower with its front. The remaining guidance is well clustered and so a non-CMC blend will be preferred. ...Surface low development over the Gulf of Mexico by Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z ECMWF and 12Z CMC Confidence: Below average The latest deterministic guidance and ensemble plots again are rather strongly in favor a low to mid level low center evolving near or north of Yucatan Peninsula by Friday that will be lifting north toward the central Gulf of Mexico by Saturday. The 00Z NAM and 12Z ECMWF solutions are the fastest, although the NAM is definitely among the deepest of solutions. The 12Z CMC is also somewhat stronger but not quite as deep as the NAM. rather deep like the NAM, but is slower to lift the system up to the north. The 00Z GFS is farthest to the east with the low and has the system over far western Cuba by the end of the period. Meanwhile, the 12Z UKMET is slowest and farthest south with the system still over the western Caribbean Sea on Saturday. The GFS and UKMET have very little ensemble support for their respective solutions and will be discounted as the majority of European, Canadian and GEFS members have the low somewhat over the central or eastern Gulf of Mexico on Saturday with several members that are actually well north up near the central Gulf Coast. The preference will be toward a blend of the ECMWF and CMC as a means of compromising on location and intensity. This will also be near the middle of the ensemble 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