Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 252 PM EDT Sun Jun 02 2019 Valid Jun 02/1200 UTC thru Jun 06/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation and Preference ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 12Z GFS/ECMWF Confidence: Average The flow is characterized by a dominant northern jet stream and trough - ridge - trough pattern across Canada and the northern United States, with a nearly pinched-off trough being dragged slowly along through the southwest U.S. and a tropical disturbance flirting with the Mexican Gulf Coast and far south Texas. Models are reasonably well clustered with these large scale features, so we will concentrate on the detail differences. The stronger flow remaining well north, removed from the low center in CA/AZ/NM, would seem to favor slower progression from the Southwest into the Southern Plains. This favors the NAM, GFS. There is, however, some indication that over time the wavelength will shorten, allowing for some acceleration toward the east. We still favor the NCEP guidance across the southern Plains, but could recommend blending the GFS/ECMWF for a more representative consensus. In the northern stream flow there are several models that produce particularly flat westerly flow through the mean ridge position in the Canadian Prairie Provinces. Given this is downwind of the mountain obstruction, we would expect to see shortwaves maintain some definition / amplitude through geostrophic adjustment, more like the 06Z GFS. Admittedly, though, the 12Z GFS trended flatter, more like the ECMWF, and the GFS-FV3 has also favored a flatter solution. Given the 12Z GFS, ECMWF are now so similar, it is convenient to recommend them as a blend preference. In all of this, the NAM is in close enough agreement to be useful, though we will rely on the global models wherever differences exist. Meanwhile, the National Hurricane Center places medium odds on tropical cyclone formation in the western Gulf of Mexico early this week. Regardless of cyclone formation, the tropical wave will contribute to a plume of rich tropical moisture moving up into Texas and adjacent OK/AR/LA by Days 2 and 3, leading to the potential for heavy rainfall ahead of the Southwest U.S. trough. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Burke