Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1255 AM EDT Thu Jun 04 2020 Valid Jun 04/0000 UTC thru Jun 07/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z NAM/GFS Evaluation Including Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-level shortwave moving through Ontario/Quebec and the Northeast through the weekend... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model blend Confidence: Average The models show similarly to one another concerning the timing and strength of a mid-level trough advancing east through southern Canada and the Northeast along with the related surface low. There are some minor differences, but overall, a general model blend works here given the differences all fall within the fairly tightly clustered ensemble guidance. ...Initial cut-off low offshore southern California, moving onshore Friday and into Great Basin Saturday with weakening amplitude... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 50/50 blend of the 12Z ECMWF/00Z GFS Confidence: Slightly above average A cut off upper low will move slowly northeast Friday and move onshore into southern California. The low opens up as it moves inland within confluent flow and this is where timing differences show up in the model guidance. The GFS has trended slower which leaves the 00Z NAM as the fastest/farthest east with the shortwave as it crosses the Rockey Mountains. The 12Z ECMWF/UKMET/CMC are fairly similar and slower than the 00Z NAM/GFS. The ensemble means seem to split the difference between the slower non-NCEP camp and the 00Z GFS, so a 00Z GFS/12Z ECMWF blend will be preferred for this system. The 12Z UKMET and 12Z CMC are similar to the 12Z ECMWF with their timing and may also be used as well along with the 12Z ECMWF. ...Closed low off British Columbia drifting south through Friday night and then off Washington/Oregon Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS, 12Z ECMWF, 12Z UKMET blend Confidence: Slightly above average Only the 00Z NAM, which is faster to take mid-level height falls eastward across the northwestern U.S. Saturday night into Sunday, differs significantly from the remaining good model clustering. However, the 12Z CMC is displaced a bit north with the closed low and does not have a rather powerful 110-130 kt upper level jet axis as far south as the well clustered 12Z ECMWF, 00Z GFS and 12Z UKMET on Sunday. Therefore, the preference is toward a blend of the 00Z GFS, 12Z ECMWF and 12Z UKMET. ...Tropical Cyclone Cristobal... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM, 12Z ECMWF closest to 03Z NHC advisory Confidence: Refer to NHC products The 00Z NAM and 12Z ECMWF air fairly similar with the track for T.S. Cristobal while also showing fairly similar strength to one another. The 12Z CMC differs the greatest compared to the 03Z NHC advisory for the track of Cristobal, with a faster timing. The 00Z GFS is also faster than NHC and a bit to the east of the NHC track, but not as significant as the 12Z UKMET which falls on the very eastern edge of the latest ensemble scatter low plots. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto