Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1127 AM EST Mon Feb 03 2020 Valid Feb 03/1200 UTC thru Feb 07/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS Evaluation with Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ ...Evolving full latitude trough over the Central US through Thu... ...Surface wave developing over the Lower MS Valley...moving into the interior Mid Atlantic late ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ Preference: 12z NAM/00z ECMWF/00z ECWMF ensemble mean blend Confidence: Average The 12z NAM/GFS are close to the consensus with the evolving positively tilted long wave trough over the Intermountain West through this evening. After that time, the 12z GFS becomes faster than the consensus, as it is not quite as deep with the evolving long wave trough over the Rockies into Central and Southern Plains. This trend continues as the full latitude trough develops over the Central US by 07/00z. The GFS has been consistently faster with this feature over the past several model cycles. By contrast, the 12z NAM remains closer to the consensus through much of the period as the trough evolves, mirroring the consistent 00z ECMWF/00z ECMWF Ensemble mean with this feature. The 00z CMC/UKMET are slower/faster with the long wave trough respectively. The surface wave developing with the long wave trough tracks from south TX at 05/12z to the interior Mid Atlantic by the end of the period. Like the mid level features, the 12z GFS/00z UKMET are too quick with the surface wave. The 00z CMC remains the slower member of the guidance envelope. Based on the above, a blend of the 12z NAM/00z ECMWF/00z ECMWF ensemble mean are preferred. Because there are some differences with the handling of the surface low across the interior Mid Atlantic before 07/00z, forecast confidence is average. ...Northern stream energy tracking from British Columbia Tue into the Northern Plains/Great Lakes Thu... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ Preference: Non-12z GFS blend Confidence: Slightly above average Short wave energy in the fast mid level flow tracks from the central British Columbia coast 0at 4/12z into the Northern Plains by 05/12z. During this time frame, both the 12z NAM/GFS are close to the model consensus. After 05/12z, the 12z GFS becomes much more amplified with the trough over the Northern Plains/ Upper MS Valley, closing off over MN/IA by 06/12z. By contrast, the 12z NAM remains close to the tightly clustered consensus, taking the bulk of the short wave energy across the Northern Plains into the Upper Great Lakes by the end of the period. Since the 12z GFS is much faster and deeper with the system (even when compared to the 00z GEFS mean), it was excluded from the preference. Thus, a non-12z GFS blend was preferred with this feature, with slightly above average confidence. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hayes