Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 135 AM EDT Tue Apr 02 2019 Valid Apr 02/0000 UTC thru Apr 05/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Shortwave trough/closed low crossing the Southeast... ...Strong Reaching the Gulf Coast/Southeast by Mon/Tues... ...Cyclogenesis near the Southeast Coast by Tues... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/12Z UKMET/12Z ECMWF blend Confidence: Average A rather compact and vigorous mid-level closed low traversing the lower MS Valley will open up into a trough that takes on a negative tilt across the interior of the Southeast on Tuesday while driving strong cyclogenesis off the Southeast coastline. The low center will lift quickly northeast up off the Mid-Atlantic coast by Tuesday night, and then offshore New England on Wednesday. The models reflect a very intense low center with rapid deepening, but there is still some model spread with respect to the low track. The 00Z NAM remains on the western side of the model guidance with the 12Z CMC now on the eastern side of it. The 00Z GFS, 12Z UKMET and 12Z ECMWF are very well clustered in between at least through about 36 hours. Thereafter, the GFS does edge the low track a little farther east and closer to the CMC as the deep low advances east of New England. The preference will be for a blend of the 00Z GFS, 12Z UKMET and 12Z ECMWF for this system. ...Surface low approaching the Pacific Northwest... ...Shortwave reaching the Four Corners by Wed... ...Cyclogenesis over the Southern Plains by Thurs... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 48 hours 00Z NAM/GFS blend...after 48 hours Confidence: Average The guidance depicts a progressive shortwave trough advancing inland across northern CA on Tuesday and then moving into the Four Corners region by Wednesday. Meanwhile, there will also be a wave of low pressure focused a bit farther north on Tuesday that will be approaching coastal areas of the Pacific Northwest and also under the influence of a northern stream trough/closed low west of Vancouver Island. The guidance overall is well clustered with the surface low evolution, and generally speaking with the height falls at least through about 48 hours. After 48 hours, the 12Z CMC/ECMWF solutions begin to lag the 00Z NAM/GFS and 12Z UKMET solutions as the energy traverses the lower MS Valley and aims for the TN Valley and Gulf Coast states. At the surface, cyclogenesis will take place over the southern Plains with low pressure advancing east toward the Red River Valley through 60 hours. This wave weakens as it approaches the lower MS Valley, but the guidance supports a frontal zone extending downstream through the TN Valley and into the Mid-Atlantic region by Thursday and Friday. The UKMET for its part appears to be lifting its warm front too far north by the end of the period. So, based on the latest trends/clustering, a general model blend will be preferred through 48 hours, followed by a blend of the 00Z NAM and 00Z GFS. ...Upper trough over the Northern Plains/Midwest Tues... ...Surface cold front crossing the Midwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The guidance support the intrusion of a new northern stream trough digging down over the northern Plains and Midwest by Tuesday along with a cold front. There is reasonably good model agreement through Wednesday as this energy then crosses the Great Lakes and portions of the Northeast. A general model blend will be preferred with this energy. ...Shortwave troughs approaching the West Coast Thurs... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z ECMWF/12Z ECENS mean/18Z GEFS mean blend Confidence: Average The models show a parade of shortwave energy/troughs approaching the West Coast on Thursday and moving inland by Friday. This will include a distinct southern stream trough moving into the Southwest, and also northern stream trough moving into northern CA and adjacent areas of the Pacific Northwest. The latest ensemble plots from the latest GEFS/ECENS member suite favors a solution closest to the 12Z ECMWF as the 00Z NAM/GFS and 12Z UKMET are more out of tolerance. The 12Z CMC for its part tends to favor the ECMWF solution. Will favor a blend of the 12Z ECMWF, 12Z ECENS mean and 18Z GEFS mean with the height falls/energy advancing toward the West Coast and inland by the end of the period. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Orrison