Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 227 AM EDT Thu May 09 2019 Valid May 09/0000 UTC thru May 12/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Exception: 00z GFS/CMC/UKMET blend across MS Valley/East after 11/12z Confidence: Slightly above average before 11/00z Average afterwards 07z update: The 00z ECMWF continues to be on the deeper side of the ensemble suite with the digging trof in the Midwest by late Sat/Sun, this continues to delay QPF axis and draw it further north into the Ohio River Valley... The 00z UKMET trended a bit deeper too but still continues (like the GFS) to press the southern stream shortwave further east. The 00z CMC has come into better alignment with the guidance and would favor the GFS/UKMET solution in the northern stream but still a bit slow with the closed low in the Southwest (but close to the ECMWF). A general model blend may suffice for much of the CONUS through day 2, but growing split on handling the southern stream shortwave on Day 3 seems to force a choice in the overall suite. Given pattern being a bit faster and convection sweeping south toward better instability, thinking the GFS/CMC/UKMET solution may be a bit more favorable on Day 3 along/east of the MS River. Still, may incorporate the ECMWF/NAM by slowing the shortwave/QPF axis a bit more than the operational GFS. Confidence remains average in this blend. ---Prior Discussion--- A fairly atypical synoptic pattern will continue across the CONUS to end this week with a broad but weakly defined trough across across the Northern Plains, evolving to a positive tilt trof as the western shortwave in the trof, retrogrades into the Great Basin by late Thursday, directing a strong Pacific wave through northern Old Mexico, while the remaining northern stream trof digs across the Midwest by Sun. Broad southwesterly flow and an open Gulf of Mexico, will continue to support convective complexes across the Northwest Gulf Coast to continue significant flooding concerns in SE TX to the Lower MS Valley. Even though the pattern is abnormal and mildly complex, there is fairly strong deterministic model guidance, including some of the timing/placement of the upscale convective complexes. The major departure is the 12z CMC which has some timing and depth issues; the main one being the very slow closed low developing in the Southwest starting around 11/00z and becoming a clear outlier by 12/00z. Otherwise the mass fields are pretty good. The 00z NAM trended a bit better with the digging trough across the Midwest on Sunday matching the 00z ECMWF a bit more than the 00z GFS and 12z UKMET, which show a slightly faster/less deep solution relative to the slower/deeper ECMWF. The only other issue in the solutions, appears to be related to timing as well, and perhaps some manifestation of the difference in the Midwest on day 3. As the undercutting Pacific trough reaches W TX around early Sat morning under good agreement (minus the CMC as noted before). As it shears into confluent flow across the Lower MS Valley, the GFS/UKMET get a bit faster and intersecting with return moisture flow and lingering frontal/outflow enhanced boundary across the lower MS valley/SE TX, the shortwave shifts more eastward along with the overrunning QPF swath. This is opposed by the slower ECMWF and 00z NAM, both suggesting stronger isentropic ascent and higher QPF axis into the lower TN and OH river Valleys late Sat into Sunday morning. Each model seems to be representing its typical late forecast bias (GFS too fast, NAM to wound up, ECMWF too slow, UKMET too strong, but too fast) and a more centralized solution both in timing, angle of QPF axis and shortwave should be employed as best as possible. As such a non-CMC blend is supported at slightly above average confidence, with only average to slightly below average confidence with the QPF axis at the end of Day 3 forecast period in the Lower MS valley into the TN/OH Valleys and Mid-Atlantic (with the fast solutions). Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Gallina