Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 239 PM EDT Wed May 22 2019 Valid May 22/1200 UTC thru May 26/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation Including Preferences and Forecast Confidence... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall CONUS Overview... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Exception: 12z ECMWF/UKMET in Pacific Northwest Day 3 Confidence: Slightly above average Average to slightly below avg. @NW Day 3 19z update: The trends in timing/placement with the lead shortwave crossing New England as well as the shortwave/closed low lifting across the Rockies into the Dakotas on Friday, has come into stronger agreement to support a stronger general model blend with this system too. The remaining uncertainty is within the Pacific northwest and northern CA on Day 3. The spread continues to widen due to the timing of the secondary shortwave/jet streak entering WA by the end of day 3, thinking the GFS may be a bit too fast and weak given more consistency/stronger trend in the UKMET and ECMWF. As such will hedge toward a ECMWF/UKMET blend for the West on Day 3 though confidence remains average to slightly below average given the spread in solutions. ---Prior Discussion--- Large scale pattern is fairly locked in with high model agreement with broad western trof with embedded weather producing shortwaves intersecting with broad southwesterly flow out of the subtropical Pacific and return moisture from the western Gulf rotating around a static strong subtropical ridge in the Southeast. WV loop shows mature cyclone over the northern Plains which is expected to consolidate and shift over the ridge dipping across New England Friday, the 12z GFS becomes a shade north and east of the strong model agreement (esp. in lowest levels) as it crosses into the Gulf of Maine 24.12z, this is minor and a general model blend can be employed with good confidence. The next shortwave in the larger scale trof is currently taking shape over California dropping into the base in the Southwest by early Thursday. It, like its predecessors, quickly shifts northeast into the central Plains consolidating over the western Dakotas early Friday, with the dry line/cold front orienting with the broad southwesterly flow aloft through the Central Plains into the Midwest. The mass differences here seem driven by the strength of the convective feedback to the intersection/triple point low through the Missouri River Valley. The ECMWF is much further east followed by the GFS/CMC, and therefore tug the overall pattern further east relative to the other guidance. Given the proximity to the fuel/instability, this seems plausible and would favor this direction/weighting over the more stalwart UKMET/NAM which can be prone to this negatively speaking, ie slightly faster/very compact strong upper level low irrespective of insolation/instability and upscale convective influence. Again a general model preference is preferred though weighting toward the GFS/ECMWF/CMC solutions. The next piece of shortwave energy is very weak relative to the prior pattern as it takes residence in the base of the larger trof, over SW CA and the California Bight by 25.00z Sat. The GFS may be a bit too deep/strong relative to the other guidance, but the overall influence in the weather pattern is negated due to the approach of the next stronger upstream system. This system is already breaking off into a closed 5H system by early Sat coming through coastal WA into OR. The UKMET/CMC and ECMWF are uncharacteristically a bit faster than the NAM/GFS still show fairly good agreement in such a dynamically strong evolution; only by the end of the forecast period does there appear some moderate differences (not bad for this time range). The 12z NAM is a bit east and north (SE OR), though the CMC may be a bit too fast/amplified very strong/closed west in N CA. So would favor something closer to a compromise with higher weighting toward the ECMWF/GFS/UKMET in the general model blend for this region...though confidence is average for this area of the country relative to the slightly above average elsewhere. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Gallina