Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 133 AM EST Thu Dec 19 2019 Valid Dec 19/0000 UTC thru Dec 22/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preference and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z ECMWF, 12Z ECMWF Ensemble Mean, 00Z CMC Confidence: Average ---06Z UPDATE--- No change to the preliminary preference. The ECMWF remained relatively consistent with the 12Z ECMWF Ensemble Mean, as did the 00Z CMC. The 00Z UKMET converged toward these models as well. ---PREVIOUS DISCUSSION--- A somewhat amplified pattern across the CONUS will become increasingly amplified over the next few days. A strong closed low will develop aloft along the Gulf Coast, with a large, positively tilted trough approaching the West Coast. In situations like this, the preference is to generally lean away from the faster wave progression bias of the GFS and NAM as an amplifying pattern tends to support slower progression of synoptic scale systems. With the Gulf Coast closed low, the trend over the past several model cycles with the GFS has been to slow it down despite the GFS and GEFS members still being faster than just about all remaining ensemble members. Given the slower trend and lack of support from other models, the preference is to lean away from the GFS (and NAM, which is similarly fast). The 12Z UKMET is showing the opposite -- it is generally on the slower end of model guidance, particularly with the Gulf Coast low. As with the GFS and NAM, it can't be completely discounted as a possibility, but the preference is to lean toward the ECMWF, ECMWF Ensemble mean, and CMC which offer an approximate median scenario and good consistency between their forecast depictions. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Lamers