Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 237 AM EDT Mon Jul 29 2019 Valid Jul 29/0000 UTC thru Aug 01/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation With Final Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Central and Eastern U.S... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average ...07Z update... Outside of smaller scale vorticity maxima placement, there were not any significant changes to the evolution depicted by the 00Z ECMWF/UKMET/CMC compared to their previous 12Z cycles over the eastern half of the nation. ...previous discussion follows... Middle and upper level flow over the CONUS through Wednesday night will be represented by ridging centered over New Mexico with troughing east of the Mississippi River and troughing approaching the Pacific Northwest. The models are in good agreement with a mid-upper level trough which will track eastward from the Upper Mississippi Valley this morning. An upper level closed low or elongated trough axis is expected to form with little movement in the vicinity of the central Gulf of Mexico early this week. There are some minor differences with this feature, but a general model blend suffices for this system through Thursday morning. ...West Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend, or blend of GEFS/ECMWF ensemble means Confidence: Slightly above average ...07Z update... The 00Z ECMWF/UKMET/CMC held consistency with their previous 12Z cycles concerning the southwestern ridge, but converged a bit with the trough approaching the Pacific Northwest Wednesday night. Therefore, there is no change in thinking with respect to the preference and a middle ground continues to be favored across the Pacific Northwest with a general model blend also favored across the Southwest. ...previous discussion follows... Good model agreement exists with the position and strength of the mid-level ridge centered over New Mexico for Tuesday through Wednesday along with a weakening upper level shortwave to reach California on Wednesday, with a general model blend recommended. Differences exist across the Pacific Northwest however, mainly on Wednesday. There is poor run to run consistency with how a closed low evolves as it slowly moves down the coast of British Columbia through mid week. The 12Z ECMWF/CMC take this feature farther inland by Thursday morning while carrying a secondary portion of energy over the eastern Pacific. Other solutions like the 00Z NAM/GFS hold onto the primary closed low near the British Columbia coast with broader troughing extending southwest into the eastern Pacific. Given the spread observed in the deterministic and ensemble guidance, along with poor consistency from run to run in the deterministic guidance, an ensemble mean approach seems best...located between the 18Z GEFS and 12Z ECMWF means. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Otto