Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 343 AM EDT Wed Apr 15 2020 Valid Apr 15/0000 UTC thru Apr 18/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Shortwave Energy Moving Across Midwest/Ohio Valley Day 2/3... --------------------- Model Blend Preference: 00Z ECMWF, ECENS mean, and UKMET Confidence: Slightly above average 07Z update: No major chances noted with the rest of the 00Z guidance for this feature on day 3. The non-NCEP guidance remains favored. ---previous discussion--- Shortwave energy moving through the Inter-Mountain West is expected to shear to the east across portions of the Midwest/Ohio Valley Friday as it becomes absorbed into the westerly mean flow. As this happens and influence from northern stream enegy over the Great Lakes, a weak surface low is forecast to develop and move through the Ohio Valley. The GFS and NAM are too progressive/north and strong with the shortwave energy and therefore have a much deeper low at the surface. The ECMWF/UKMET and ECENS mean has been consistently a more favorable solution and remains the preferred blend for mass fields and QPF for this time frame. Western/Central CONUS -------------------- Model Blend Preference: General model blend day 1/2, 00Z ECMWF/UKMET/ECENS mean blend day 3 Confidence: Slightly above average 07Z update: No significant changes with the rest of the 00Z guidance. The 00Z ECMWF continues to show fairly good consistency and will be incorporated into the latest model blend preference. ---previous discussion--- Anomalous upper level ridge over the eastern Pacific begins to break down as a shortwave trough undercuts its and then closes offshore the western U.S. coast. Through 48 hours, there is very good agreement with the depth and progression of this feature and even into day 3 as the system opens up over the Southwest, there is fairly good agreement. The UKMET is a bit faster than the rest of the guidance and now the GFS is on the slower side but for the most part, a general model blend for this feature is preferred. Shortwave energy will also move through the northern Rockies and then across the Inter-Mountain West in the day 1/2 time frame. The 00Z GFS/NAM quickly become unusable after about 36 hours as the shortwave is too strong and too fast compared to the rest of the guidance and the ensemble means. Especially by day 3 /Friday/ the GFS begins to shear the shortwave too strongly to the east, stringing out the vorticity lobe faster than the remaining guidance. For these reasons a ECMWF/ECENS mean/UKMET is preferred for most of the West D3 as they are consistent and match well to each other. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor