Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1145 PM EST Mon Mar 04 2019 Valid Mar 05/0000 UTC thru Mar 08/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation Including Preference and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep trough over the Great Lakes/Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The 00z GFS/NAM continue with high continuity for the remaining deep trough through the Great Lakes into the Northeast. Even smaller scale timing/wave depths have coalesced over the last few cycles to keep an above average confidence in a general model blend. ...Deep closed low center near 32N 143W... ...Arriving across CA by Wed... ...Shearing downstream across the central Plains on Thurs... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 60 hours (7/12z) 12z UKMET/ECMWF and 00z GFS afterward Confidence: Above average before 60hrs becoming Slightly above average thereafter GOES-17 WV detects a deep compact closed low near 32N139W with a broad downstream warm conveyor belt extending from the subtropics before broadening east of 130W at this time. Models have become much more consistent in the track, maintenance of the strength of the wave through Wed, with only the UKMET showing some low to mid-level northward adjustment; being a bit more aggressive with the faster timing of binary interaction in closed low SW of Vancouver Island). By 00z Wed, a secondary northern stream jet streak/vort center rotates around the base early Wed to enhance heavy rainfall and snows across the terrain in the Intermountain West and Central Rockies. This warm conveyor is fairly well agreed upon too to have fairly good confidence through the Day 2 period. As the warm advection moves into the Central Plains, Thursday, the 00z NAM and GFS appear to have strongest upglide (shortwave). However, the 00z GFS has trended weaker shearing through the larger scale ridge into the Ohio River Valley by Fri. The ECMWF/CMC are faster to weakening the warm advection and eventually focus on intersection of the return moisture coming out of the Gulf into the Ozarks to W TN Valley by the end of the forecast. Here a compromise is suggested favoring weaker/sheared flow through the ridge but holding onto some of the intensity given the overall strength of the warm conveyor. As such a blend of the 00z UKMET/ECMWF with the weaker 00z GFS seems a good compromise both in placement of the QPF swath as well a magnitude after 60hrs (07/12z). Given model sensitivity is moderately high for slight differences in moisture flux/depth of the 5H wave; though models are fairly agreeable in placement/timing; confidence is slightly above average after 60hrs. ...Deep closed low near the Pacific Northwest... ...Undercutting shortwave trough approaching CA on Thurs... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend (weighting to CMC/GFS) Confidence: Average The initial binary interaction with the two compact vort centers near (SW) of Vancouver Island continues to come into some good agreement, the 12z UKMET is a bit faster, digging south interacting with the first southern stream closed low on Wed with limited overall model differences becoming a fairly concentric closed low again centered near the mouth of the Strait of Juan de Fuca by 72hrs. Another strong progressive closed low will advance toward the Pacific Coast (reach 130W) around the same time. Here differences start to manifest, as the upper low breaks down a bit, with the upper low becoming a bit less unbalanced. The 00z GFS and 12z CMC suggest very strong leading wave/closed feature into Alberta by 84hrs while the 12z UKMET/ECMWF favor the western portion of the low, maintaining something more concentric. Interestingly, this leads the ECMWF to tighten the flow along the southern side accelerating the progressive Pacific low into the West faster than most ensemble solutions. Interestingly, the CMC does the same thing with a bit of increased phasing with the western side of the off-balanced WA/Alberta closed low. Both becoming increasingly sheared elongated through the Great Basin by 84hrs. The 00z GFS/NAM are both uncharacteristically slower, NAM more so and a bit stronger too. Ensembles would suggest the ECMWF may be a bit too fast and the UKMET a bit slow, but there seems to be be more cycle to cycle vacillation than a consistent trending toward a common solution. This suggests support toward a general model blend, weighted toward the CMC/GFS as more central solutions even though a blend like this spreads out the fields and weakens the meteorological signal. As such confidence is average in the blend. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina