Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 134 PM EDT Wed Jun 13 2018 Valid Jun 13/1200 UTC thru Jun 17/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS evaluation...with preliminary preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall model diagnostic analysis for the CONUS... Preference: General blend; greatest weight on 12Z GFS; 00Z ECMWF Confidence: Slightly above average The pattern over the CONUS is gradually shifting to one with stronger synoptic forcing: a trough over the Northeast (reinforced by several shortwaves), a trough in the West with an upper-level low digging down the West Coast, and a broad upper level anticyclone shifting from the Southern Plains into the Mid Mississippi River Valley. The Northeast trough is forecast to exit into the western Atlantic for the weekend as mid-upper level ridging gradually slides east from the MS valley. Out West, as one shortwave (currently over the Pacific Northwest) advances east-northeastward into south-central Canada by Friday morning, a second upper level system will close off over the Northwest in its wake, setting up a longwave trough axis over the western U.S. for the weekend. The latest model guidance shows decent agreement on all of these larger scale features, with minor timing differences noted with the exiting Northeast trough axis which translates to latitude differences with the associated cold front into the Southeast. The small scale spread noted in the latest deterministic/ensemble guidance suggests a general model blend can be used here. Smaller scale vorticity maxima, especially across the Southeast, show larger differences, with no single model standing out as an outlier and with poor run to run continuity which lowers confidence in the details. The preference here is for an ensemble mean approach weighted to the mass fields of the 12Z NAM and 00Z ECMWF. Elsewhere, a blend of the 12Z GFS and 00Z ECMWF shows good agreement to the ensemble means and is well supported in the past few cycles of the GFS and ECMWF. ...Tropical Storm Bud / Remnant circulation... See NHC for official forecasts for Bud Closest Model Proxy: 12Z NAM/00Z ECMWF blend The 15Z NHC advisory on Bud shows good agreement to the 12Z NAM/GFS with the 00Z ECMWF/UKMET/CMC initially a bit west of the track near the Baja peninsula. Afterward, as the mid-level reflection of Bud continues northward into the Southwest U.S., there are some timing differences. However, the 12Z GFS appears to be too strong with this mid-level reflection over the southern Rockies Saturday night, which is a change from its previous cycles. Here, a 12Z NAM/00Z ECMWF blend is more in line with the synoptic scale thinking for this area of the country, after the surface circulation of Bud as dissipated. For official forecast updates on Hurricane Bud, please refer to the National Hurricane Center forecasts. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto