Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 146 PM EST Mon Feb 11 2019 Valid Feb 11/1200 UTC thru Feb 15/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Final Preferences and Confidences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: (East) 12Z ECMWF/NAM/UKMET blend (West) 75% 00Z ECMWF / 12Z GFS blend Confidence: Average except out West (Slightly Below Average) ...19Z update... Across New England, the 12Z CMC trended close to the remaining, well clustered deterministic guidance concerning secondary surface low development Wednesday morning. Relatively minor mass field differences remain with a 12Z NAM/ECMWF/UKMET blend near the middle of the latest guidance. Out West, the 12Z CMC remains similar to its previous 00Z cycle with a lead shortwave reaching the West Coast Wednesday night, while the 12Z UKMET trended east a bit closer to the preference and the 12Z ECMWF trended away/offshore with the closed low off of the West Coast. The 12Z ECMWF shifted even farther offshore compared to the near outlier 00Z UKMET and remains on the outside edge of the 00Z ensemble spaghetti height envelope. The uncertainty remains above average out West given the large chances continue from cycle to cycle, but the final preference is to stay with the better ensemble agreement near the 00Z ECMWF and 12Z GFS. ...previous discussion follows... A general trough-ridge-trough pattern will be in place across the lower 48 through the middle of the week. The sensible weather impacts for the central to eastern part of the nation will be tied to a shortwave trough which will move through the Great Lakes and Ohio Valley Tuesday night and New England on Wednesday. A weak and slow moving and compact closed low is expected to move across south-central Canada through Thursday while a pair of powerful shortwaves affect the western U.S. with a broad low amplitude ridge located between the East and West Coast systems. There is general good agreement with the East Coast trough and a secondary surface low forecast to organize over New England early Wednesday when discounting the 00Z CMC. The 00Z CMC is a western outlier with its secondary low development 12Z Wednesday given differences in its handling of an upstream, small and compact closed low over southern Manitoba which draws the New England shortwave back to the west. There is good ensemble agreement encompassing the 12Z NAM, 12Z GFS, 00Z ECMWF and 00Z UKMET for the secondary surface low affecting New England. Among the non-00Z CMC models, there are minor differences with the timing/amplitude of the shortwave and surface low but a blend led by the 00Z ECMWF and 12Z NAM appears most favored at this point. Out West, the models differ with the handling of the southern portion of a positively tilted trough offshore of the Pacific Northwest Tuesday night into Thursday morning. Some models (12Z NAM, 00Z UKMET) close off a mid-level low and keep the system offshore while others are less aggressive with the energy digging into the base of the trough allowing the shortwave to move inland across the West Coast Wednesday night (12Z GFS, 00Z ECMWF, 00Z CMC). There is poor run to run continuity in the deterministic guidance here but the latest ensemble spaghetti heights show the 00Z UKMET and 12Z NAM as near outliers with hanging the shortwave offshore Thursday morning. There are still large differences inland across the interior Northwest, but there is better support for a solution near the 00Z ECMWF, which is a bit deeper than the 00Z ECMWF mean but less amplified than the 12Z GFS and 00Z CMC to some degree. Otto Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto