Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 241 PM EDT Wed Jul 18 2018 Valid Jul 18/1200 UTC thru Jul 22/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z model evaluation including preference and forecast confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference in Eastern US: 12z UKMET/ECMWF blend Confidence: Slightly below average Preference in Pacific NW US: Non-UKMET blend Confidence: Average ...Overall Model Analysis for the CONUS... 19z Update: The higher uncertainty has resolved somewhat with the UKMET/ECMWF trending faster across the Midwest as presented by the NAM/GFS initially, yet both remain slower than the NAM/GFS. The CMC is the clear outlier and is much further north. This change in transition has shifted the timing of the Gulf to East Coast wave further west, but the GFS is a clear outlier fast and west while the UKMET/CMC and ECMWF still lag the NAM. Would favor something closer to the ECMWF for this coastal wave and close to the UKMET/ECMWF and perhaps some GFS for the Ohio Valley. As for the west coast, the ECMWF is a bit less sheared and more progressive than the GFS and paired with the 12z CMC fairly well. Only the UKMET is more compact and faster, as such would shy away from the UKMET. Confidence ----PRIOR DISCUSSION---- Models continue to show the greatest differences with a trough digging into the Upper Midwest by late in the week, with the NAM standing out from the main deterministic suite, being faster and closing off a new upper level center in the Ohio Valley by Sat into Sun. The GFS and UKMET trend this direction (GFS faster) while the ECMWF/CMC slide more eastward as the older center broadens over the Central Great Lakes. If you will, a typical timing orientation only exacerbated by the larger spreads. This timing/strengthening also draws the warm conveyor belt and associated shortwave out of the eastern Gulf of Mexico, with moderate spread. The NAM/GFS are quick and tucked further west to the coast compared to the ECMWF/UKMET and CMC. The further eastward shift, allows the CMC to be quite amplified due to orientation with the upper jet/divergence maxima, making it a bit less desired at this point. The catalyst for the model spread appear to be related to the strength/magnitude of upscale feedback from convection development this evening over the Mid-Missouri River valley. The NAM develops a complex that digs south-southeast across NEB toward the Low MO-Valley today, with a stronger 3H jet rounding the base of the trof earlier. This is followed by the GFS and so on... the Hi-res CAMs would suggest that the NAM is an outlier but modest spread including within the HREF mean/NBM (at least in QPF fields) suggest a compromise between the UKMET and ECMWF may be a good suggestion, but at lower (slightly below average confidence). Further west, the closed low in the Gulf of AK reaches central BC by late Fri with good agreement, the spread begins to increase based mainly on if/how far east the main inner core before it breaks down a bit and stretches in the ridge weakness over the west coast (in the larger scale). Timing, once again, becomes the main difference though compact/vort centers, manifest as well. The NAM is fast and the UKMET is very compact with the trailing shortwave. The CMC is slow to stretch, while the ECMWF/GFS are more inline with each other and the ensemble suite (trends in the day to day ensemble suite) that would suggest a better overall blend. Confidence is average for this area. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina