Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1245 PM EDT Sun Sep 22 2019 Valid Sep 22/1200 UTC thru Sep 26/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep trough crossing the Upper MS Valley tonight, Great Lakes Monday, Northeast Tuesday, Canadian Maritimes Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Multi-model consensus, close to the 12z NAM/GFS Confidence: Above average Model differences with the trough are rather small through tonight as the energy crosses the Upper MS Valley, the Great Lakes on Monday, and northeast on Tuesday. The primary differences develop as the mid level circulation departs New England on Wed, with both timing and track differences gradually growing. A consensus approach is suggested until better clustering develops over the Canadian maritimes on Wed. ...Upper trough digging into the West by Monday... ...Closed low evolution over the Southwest by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 00z ECMWF/12z GFS/00z UKMET Confidence: Slightly above average Regarding the second trough moving into the West, the model guidance is well clustered and in good agreement with respect to timing and depth through most of Monday. The model majority shows a closed 500 mb low developing as the energy digs south into the Southwest on Tuesday. The low drifts south to southwest near the Mexican border Wed, possibly over the northern Gulf of CA or just a tad east of here over northwest mainland Mexico Wednesday. The 06Z GEFS mean and 12z Nam are still farther east with the closed low solution, so differences are not yet completely resolved. All of the models do indicate some interaction with the remnant moisture and energy associated with weakening Tropical Storm Lorena which is expected to lift across northwest Mexico Sunday before then dissipating Sunday night. Given the much better deterministic clustering with the closed low evolution among the ECMWF/GFS/UKMET, the preference will be to blend these solutions. ...Upper trough over the northern Plains by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Multi-model consensus of 00z ECMWF/00z UKMET/12z GFS Confidence: Above average The models have good agreement overall with the details of a northern stream trough and associated cold front crossing the northern High Plains by Tuesday and upper Midwest by Wednesday. Minor timing and amplitude/phasing differences exist Tue night and Wed among the global models and their ensemble means. The solutions cluster well so a consensus approach to blend the ECMWF/GFS/UKMET should work well. ....Upper trough approaching Vancouver Island Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Multi-model consensus of 00z ECMWF/00z UKMET/06z GFS Confidence: Slightly Above average The models indicate a 700 mb-500 mb wave develops west of Vancouver Island and moves east towards the coast on Wed, possibly extending as far south as northern Wa State. The 12z NAM/06z GFS/00z UKMET/00z ECMWF all show the wave, with typical timing difference from model to model and from one gfs run to the next. The NAM stands out with lower 700 mb heights than other solutions, so less weighting should be given to the NAM, given confluent flow. Use of a ECMWF/UKMET/GFS consensus is recommended due to a similar amplitude and track of the 700 mb wave. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Petersen