Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 226 AM EDT Sun Sep 08 2019 Valid Sep 08/0000 UTC thru Sep 11/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend; less weight on 00Z GFS/NAM Confidence: Average ---06Z UPDATE--- No change to the preliminary preference. With the arrival of the remainder of the 00Z deterministic model runs, the 00Z GFS seems to be further east with the position of the western U.S. trough than any of the other models including the GEFS mean. For this reason, less weight will continue to be placed on the GFS and the NAM (which is more amplified with the trough relative to other models). ---Previous Discussion--- Models are in good agreement on an amplification of the synoptic pattern across the CONUS over the next several days, with a trough in the western U.S. and a ridge in the east. The deterministic models are reasonably well clustered and heights at several pressure levels are within the ensemble envelope. The ECMWF ensemble 500mb height spread is generally near or less than the previous 30 day average in most areas, with the exception of the base of the trough in the western U.S. (related to uncertainty on the amplitude of the trough). Given these factors, a general model blend is preferred in most areas. One of the larger QPF differences exists over the Mid-Mississippi Valley and interior Southeast. The 00Z GFS and NAM show more widespread and heavier rainfall on Tuesday and Tuesday Night in these regions, while the other global models have limited rainfall. The preference in these areas is to lean toward the 12Z ECMWF, CMC and UKMET, as the region will be underneath an expanding ridge. While some convective rainfall is possible, the blend will be weighted toward models showing drier scenarios. Otherwise, model precipitation forecasts are fairly similar, which is consistent with the overall agreement with the mass fields. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Lamers