Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 256 AM EDT Sun Mar 24 2019 Valid Mar 24/0000 UTC thru Mar 27/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation With Preferences/Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Plains closed Low shearing into Ohio Valley early Mon across Southeast Tues ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average 07z update: No major differences noted with the rest of the 00z guidance now available. The preference for a non-NAM solution still looks good. ---previous discussion--- Current mid/upper level closed low over the central Plains is initialized well by the current suite of model guidance. As the feature opens/weakens in the next 24-48 hours over the lower OH Valley, the latest guidance has it pushing as an open wave across the Carolinas Monday night. The NAM remains the furthest south/southwest with this feature as it digs across the Southeast US, though the 12z UKMET shows somewhat similar look. The CMC/ECMWF/GFS all have similar solutions, bringing the axis of the wave across the central Carolinas by 06z on the 26th. Overall, a blend incorporating most of the guidance except the NAM should suffice for the mass fields with this feature. Shortwave moving through the Great Basin/C Plains to Southeast Sun-late Tues ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00z GFS/NAM/CMC/UKMET blend Confidence: Slightly below average 07z update: The 12z ECMWF trended more amplified with the shortwave crossing through the Southeast US, even closing off over northern FL by early Wednesday morning. This is different from the rest of the operational 00z model guidance and also is not represented much by the ensemble guidance. The 00z CMC and 00z UKMET have more similarities with the GFS and NAM, so for now, will show a preference for a non-ECMWF blend, especially toward the end of the forecast period. ---previous discussion--- A piece of energy breaking off the large gyre off the west coast will rotate through portions of the central Rockies through tonight into Sunday before crossing the central Plains and eventually portions of the Southeast US by mid-week. There is not a lot of phasing with this feature and the lagging shortwave discussed above, but the two do work to keep troughing in place across the Southeast US and mid-Atlantic region. Here the trough should push further south, reaching northern Florida by Tuesday night. The NAM is now more similar to the 12z ECMWF while the GFS is not as deep (weaker) but not nearly as much as the CMC (which is slower and weak). Large Pacific Gyre's First Wave Entering Northwest Monday; Main Core Nearing Northern CA by Late Tuesday ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend (weighted toward 00z GFS/ECMWF) Confidence: Average 07z update: It seems like the 00z ECMWF/CMC/UKMET want to hold back the main gyre from moving onshore about 6-12 hours later than what the GFS and to some degree the NAM advertise. Though, the differences are relatively minor and the sensible weather impacts are probably similar. The first piece of energy moving into the Pacific Northwest has fairly good agreement as well. So for now the preference for a general model blend with some weight given to the ECMWF/GFS to wash out their biases seem reasonable at this point. ---previous discussion--- GOES-W WV imagery shows compact closed low around 49N, 149W currently and this large gyre will slowly advance eastward toward the western US coast through the forecast period. Pieces of energy will break off and move onshore but the main core of the system will likely brush the western US coast late Tuesday or Wednesday. The first piece of energy arrives Monday across the Pacific Northwest and for the most part, the latest model guidance is in reasonable agreement with this feature as it hugs the coastline then moves into southern British Columbia. Outside of the UKMET, the timing and orientation of the upper level pattern is fairly similar, while the UKMET is slower and also slightly more amplified with its axis. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Taylor