Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 221 AM EDT Sat May 11 2019 Valid May 11/0000 UTC thru May 14/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Exception: Non-GFS blend in Mid-Atlantic after 13/18z Confidence: Slightly above average 07z update: Small adjustments were noted with the 00z ECMWF/UKMET/CMC, particularly with the shortwave moving through the Ohio Valley Monday with suggestion of increased negative tilting leading to a slightly strong but also further north coastal cyclogenesis. The NAM/GFS both suggest this, but as noted before, the GFS was atypically slow and further west. The 00z CMC showed the greatest improvement with increased strength to the closed low as a whole and adjusting along with the other guidance a bit north toward late Monday into Tuesday. This suggests a general model blend can still be employed with slightly above average confidence with the exclusion of the 00z GFS with the coastal low late Monday into Tuesday. Elsewhere the mass fields continue to be in strong agreement. ---Prior Discussion--- Large scale synoptics continue to remain in solid model agreement. The large zone of southwesterly flow across the Western Gulf states into the Mid-Atlantic with embedded weak/subtle shortwaves and/or convectively induced MCVs lifting northward is fairly agreeable as well. It is generally collocated with deep moisture plume along/south of ill-defined frontal zone, though as the northern stream shortwave amplifies across the Northern Plains into the Midwest by later today, some slower guidance, such as the ECMWF continue to lift the front back north and therefore the QPF axis. Still overall agreement in the orientation/placement is getting better overall. As for the closed low and associated surface low that does develop in the upper Ohio Valley by Monday, there is strong agreement. Only by the end of Day 3 do we see a divergence in any of the main guidance members. The 12z CMC becomes weaker and starts to open up the mid-level trof and shift the surface wave/developing coastal low a bit further south, enough so to suggest remove it after 13/12z. Similar but on the opposite side of the scale, the 00z GFS seems to atypically deepening the closed low and subsequently shifted the coastal low development back closer to the coast away from growing consensus. Looking at the QPF output, this swing of a greater negative tilt and intersection with moisture/instability supports a upscale growth of a convective complex near the low, while possible, being atypical of the GFS, would favor shifting toward the GEFS mean as a better solution for the end of Day 3. The other major synoptic feature is the closed low that has formed in the California Bight and its subsequent tracking across N Mexico before weakening as it marches into West Texas by late Monday. Interestingly, while the guidance is very agreeable, the two strongest solutions (slower to breakdown)...00z GFS and 12z ECMWF, are strongly agreeable in mass fields but show separated areas of convective development in the return flow. Each have support from typical compatriots: NAM/UKMET to the GFS and the CMC to the ECMWF, and in general typical biased setups. As such a general model blend will be preferred at slightly above average confidence. Largest spread in mass fields is related to the amplitude and slight timing differences of the approaching Pacific trough, but the bulk of sensible weather effects are not close enough to support one over another in the short-term forecast. So please refer to the WPC medium range discussion PMDEPD for more details. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Gallina