Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 238 AM EDT Sun May 31 2020 Valid May 31/0000 UTC thru Jun 03/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Initial Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Upper level trough and cold front across the Eastern U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 00Z Tuesday, then 12Z ECMWF/GFS/UKMET blend Confidence: Above average An amplified upper level trough will continue to build in across the eastern U.S. through the beginning of the week, with the surface cold front continuing to move farther offshore and a high quality airmass settling in across much of the region. Similar to last night, the models are in very good agreement through about 00Z Tuesday with the CMC remaining slightly weaker with the trough. By Tuesday morning, an upper low is likely to evolve from the trough over the Nova Scotia region, with the GFS and UKMET indicating the best potential for this by 00Z Wednesday. A blend of the ECMWF, GFS, and UKMET should work well beyond 00Z Tuesday Upper level low slowly lifting from northern Mexico into the southern Plains Saturday-Tuesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The models are in generally good agreement indicating a broad upper low lifting north from northern Mexico into West Texas by Tuesday morning, before continuing northeast towards Oklahoma on Tuesday night. There is not much of a surface reflection of this in terms of the sea level pressure fields. A general model blend will suffice for this upper level low and trough. Shortwave lifting across the Pacific Northwest and then across southern Canada ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend Confidence: Average Overall, models are in good agreement showing a strong shortwave over Oregon and lifting northeast across Washington and then Alberta by Sunday night. Models remain in good agreement into early Monday as the system continues farther east across south-central Canada. Significant model differences do not evolve until early Tuesday as system begins to move south of Hudson Bay. As the system begins to round the top of the upper ridge, the UKMET becomes a noted outlier with a closed system developing south of Hudson Bay and much slower than the other guidance. Upper level trough moving from the Pacific Northwest to the northern Plains and Upper Midwest Monday-Tuesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 12Z Monday then, GFS/ECMWF compromise 12Z Monday-00Z Wednesday Confidence: Average With respect to timing, the models are in generally good agreement through early Monday as the system moves east from the eastern Pacific into the Pacific Northwest. However, differences quickly develop as the system moves downstream, with the UKMET, ECMWF and the 00Z EC Ensemble Mean becoming notably faster than the NCEP guidance through the northern Rockies into the Plains and Upper Midwest. While the GFS is still among the slower solutions, it has trended faster compared to its 00Z and previous 12Z solutions. And while still faster than the GFS, the 12Z ECMWF is slower than its 00Z run, suggesting the two models may be moving toward a consensus. Cutoff low developing west of Southern California and northern Baja Monday-Tuesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: UKMET/ECMWF/12Z EC Ensemble mean Confidence: Average Energy dropping southeast across the eastern Pacific is expected to develop a closed low off of the Southern California and northern Baja coasts early next week. Latest guidance shows some differences with respect to the position of the low's center, with the NCEP guidance generally a little east of the UKMET, ECMWF and the 12Z EC Ensemble Mean. Trends in the GFS support leaning toward the UKMET, ECMWF and 12Z EC Mean. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hamrick