Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1214 AM EDT Sun Mar 31 2019 Valid Mar 31/0000 UTC thru Apr 03/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation With Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep trough lifting through the Northeast... ...Cold front crossing the Eastern Seaboard... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show very good agreement with the details of the deep upper trough lifting up across the Northeast through Sunday, along with the attendant cold front which will cross the Eastern Seaboard. A general model blend will be preferred as a result. ...Four Corners to Southern Plains trough/closed low... ...Reaching the Gulf Coast/Southeast by Mon/Tues... ...Cyclogenesis near the Southeast Coast by Tues... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/12Z ECMWF blend Confidence: Average A trough and weak associated closed low over the Four Corners region will eject southeast across the southern Plains through Monday. On Tuesday, the energy will be traversing the Gulf Coast states and moving toward the Southeast. This will drive cyclogenesis along a frontal zone draped from the eastern Gulf of Mexico northeast across the FL Peninsula and up offshore the Carolinas. The dominant area of low pressure is expected to emerge just offshore of the Southeast near coastal areas of northeast FL with low pressure then lifting northeast offshore of the Carolinas by early Wednesday. The 00Z NAM is the strongest solution with the closed low/trough that ultimately swings through the southern Plains and it hangs onto stronger height falls as it crosses the Gulf Coast states and Southeast U.S. which helps to drive cyclogenesis that tucks in closer to the East Coast on Tuesday. The NAM is an outlier solution though as the global models led by the 00Z GFS, 12Z UKMET, 12Z CMC and 12Z ECMWF are all farther east and generally well off the East Coast on Tuesday, although the UKMET certainly appears to be an easterly outlier by comparison. There is still some ensemble spread with the details of how close the low pressure will tuck in toward the East Coast, and there has been a stronger trend seen collectively with the guidance over the last 24 hours, but the NAM and even to a lesser extent the CMC appear too far west. The best ensemble support would favor a consensus of the GFS and ECMWF, and a blend of these solutions will therefore be preferred. ...Trough/Low approaching the West Coast on Mon... ...Surface low approaching the Pacific Northwest... ...Energy reaching the Four Corners by Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/12Z UKMET/12Z ECMWF blend Confidence: Slightly above average The guidance depicts a fairly compact closed low approaching northern CA by late Monday which will be gradually opening up into a trough axis Monday night through early Tuesday while advancing inland. By Wednesday, this open trough will reach the Four Corners region. There will also be a wave of low pressure focused a bit farther north 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 00Z NAM is overall a tad stronger than the global model suite with the height falls crossing northern CA and toward the Four Corners region, although the 12Z CMC does become a bit of a weaker outlier by Tuesday and Wednesday as the energy advances farther inland. Regarding the surface low, the guidance is actually fairly well clustered with modest spread regarding the track of it. Overall, there is better ensemble support for a consensus of the 00Z GFS, 12Z UKMET and 12Z ECMWF solutions, and so a blend of these models will be preferred. ...Upper trough over the Northern Plains/Midwest Tues... ...Surface cold front crossing the Midwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend...through 60 hours 00Z GFS/12Z UKMET blend...after 60 hours Confidence: Slightly 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 with this height falls through about 60 hours, including the details of a cold frontal passage across the Midwest and with surface low pressure over south-central Canada. However, beyond this time period, the model spread increases as the 00Z NAM and 12Z CMC begin to diverge with the south-central Canada low evolution relative to the 00Z GFS, 12Z UKMET and 12Z ECMWF. The 18Z GEFS mean and 12Z ECENS mean tend to favor the GFS/UKMET clustering more so than the ECMWF at this point, and so after 60 hours a blend of the 00Z GFS and 12Z UKMET will be preferred. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Orrison