Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 152 AM EST Fri Jan 25 2019 Valid Jan 25/0000 UTC thru Jan 28/1200 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 00z GFS/FV3/CMC blend in southern stream/Gulf Confidence: Above average Slightly below average in southern stream/Gulf 07z update: The 00z non-NCEP guidance brings a mixed message. The positive: The 00z ECMWF/CMC both trended a bit less deep, slower crossing the Great Lakes with the initial surface wave Sunday, matching the GFS/NAM fairly well, which also allows for much better track/QPF agreement with the clipper system at the end of Day out of the Dakotas into IA. Only the 00z NAM is a bit too fast overall, but still not too bad. However, the negative is within the southern stream, where the 00z ECMWF significantly shifts further south digging out the base of the trof. This further delays the wave emerging into the Gulf but also leads to a deeper, slower wave crossing FL, looking more like a known negative feedback with the operational ECMWF. While, the CMC is similarly wound up, it is more progressive and generally matches the timing of prior runs/ensemble suite and 00z GFS/GFS-FV3. The 00z UKMET is slower than the CMC/GFS but shows similar evolution/shape to the GFS/FV3 as well as the NAM (which is clearly too fast in the suite). As such will favor a CMC/GFS/FV3 blend in the southern stream/Gulf of Mexico but given the larger spread confidence reduced to slightly below average for this region (inclusion of the 24.12z EC or ECENS mean may solidify blend a bit more). ---PRIOR DISCUSSION--- Highly amplified pattern with broad global trof centered near/south of Hudson Bay and ridge directing Pacific shortwave energy well into SE AK, leads to fairly good model agreement through the next few days. As the central hub of cold air drops into Ontario/Northern Great Lakes by late Sat into Sunday, two smaller peripheral shortwaves will track across the MO Valley into Deep South/TN Valley as well a southern stream wave will emerge from NE Mexico, generally phasing across the Gulf producing a very flat, Miller-A wave signal across S Florida into the Sargasso Sea/North Atlantic by Monday, while a surface cyclone deepens across Ontario. Model spread is modest here, with typical model biases manifesting. The ECMWF and CMC are generally slower especially across the Great Lakes while a bit less phases across the Gulf leading to a slower more amplified wave north of the Bahamas, while the NAM/GFS/UKMET are slightly faster. Yet, with these differences, only start/end time differences seem to be the largest differences in QPF for a prolonged rainfall event Sat-Mon in FL. As the next, stronger shortwave drops out of NW flow, by Monday, the guidance is quite agreeable as well until about 28.00z Monday, as downstream slower solutions (ECMWF/CMC) delay eastward progression and support a further southward dive of the surface wave/cold air across the Midwest 12z Monday. Here the 00z NAM/GFS turn eastward through IA/N IL with the surface wave because the downstream wave was already north and exiting faster relatively to the ECMWF/CMC. Ensemble suite, trend, or overall weather pattern does not favor one camp/solution over another...falling more into traditional negative biases. As such a solution between the NAM/GFS and the ECMWF/CMC is preferred; and with no perfect representation in the ensemble means/deterministic guidance to be had a general model blend will be preferred but at slightly above average confidence. (please note: an arithmetic blend is NOT preferred give it will smear out the solution but a blend that recenter the wave/features toward a 50/50 position is desired). Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina