Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 303 AM EDT Tue Jul 17 2018 Valid Jul 17/0000 UTC thru Jul 20/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Model Analysis for the CONUS... Overall Preference: 00Z GFS; 00Z ECMWF; 00Z CMC Blend General Confidence: Average ---06Z UPDATE--- No change to the preliminary preference or reasoning. The UKMET and NAM still show similar biases relative to the other deterministic models and ensemble means as discussed below. ---PREVIOUS DISCUSSION--- Models are in good agreement through Wednesday, but then greater differences begin to evolve with a trough moving through the Northern Plains and into the Upper Midwest, and how the pattern evolves downstream over the Eastern US. The 00Z NAM and 12Z UKMET are exhibiting the most significant differences from model consensus, and have been discounted from the preference. The NAM carries more mid-upper level vorticity into the Southeast and this results in more amplification to the broad downstream trough over the region. Its heights aloft are generally lower than most NAEFS and ECMWF ensemble members. On the flip side, the UKMET concentrates most of its mid-upper level vorticity in the Upper Midwest, resulting in a stronger cyclone there, and higher heights along the East Coast relative to most ensemble members. Therefore, the preference is for a blend of the GFS, ECMWF and CMC, which show reasonably good agreement and are closest to the available ensemble means. Forecast confidence is only rated as average, as the model differences are a little more notable than in recent weeks. Most uncertainty is in the eastern half of the country, with higher confidence (given better mass field agreement) in the West. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Lamers