Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 303 PM EDT Sun Mar 31 2019 Valid Mar 31/1200 UTC thru Apr 04/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation With Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep trough lifting through the Northeast tonight... ...Cold front crossing the Eastern Seaboard... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show similarly with this system. No significant changes were noted the 12Z ECMWF/UKMET/CMC compared to their previous 00Z cycles. ...Four Corners to Southern Plains trough/closed low... ...Reaching the Gulf Coast/Southeast by Mon/Tues... ...Cyclogenesis near the Southeast Coast by Tues... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z NAM blend Confidence: Average ...19Z update... Minor changes were made by the 12Z ECMWF/UKMET/CMC, with the ECMWF nudging slightly toward the coast and north, while the UKMET trended north near the 12Z GFS as the low moves up the coast. The 12Z CMC also adjusted to near the previous preference, so therefore, the 12Z NAM is the only model that stands out enough with a more westward track to be excluded from the overall preference. The 12Z ECMWF may be a bit too far west, but when blended with the remaining deterministic models should result in a suitable blend. ...previous discussion follows... Ensemble spaghetti heights and low plots have shown a slight trend to be faster and north with the surface low. Through 00Z/03, the 00Z ECMWF is closest to the best ensemble clustering while the 12Z NAM and 00Z CMC are closer to the Southeast coast. The 12Z GFS is slightly farther offshore through 00Z/03 while the 00Z UKMET is a bit south of the better model clustering. Beyond 00Z/03 and up until 00Z/04, the 00Z ECMWF and 12Z GFS show the best agreement with the latest low clustering off of the northern Mid-Atlantic and New England coasts, with the ensemble spread largely north-south versus west-east. ...Trough/Low approaching the West Coast on Mon... ...Surface low approaching the Pacific Northwest... ...Energy reaching the Four Corners by Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/ECMWF/UKMET blend Confidence: Slightly above average ...19Z update... The 12Z CMC slowed down and is more amplified compared to its previous run but is now toward the slower side of the remaining guidance. The 12Z UKMET came south a bit along with a slight nudge south in the 12Z ECMWF. A blend on the 12Z UKMET/GFS/ECMWF forms a good compromise with this system. ...previous discussion follows... Ensemble spaghetti heights and low plots show the best overall blend for this system is a 12Z GFS/00Z ECMWF blend. The 00Z CMC stands out from the remaining consensus with a flatter shortwave into the Four Corners region through early Wednesday. Outside of the differences in the upper trough, a surface low will develop across the southern high plains with a front draped northeastward through the Midwest. Some latitude differences exist with the frontal boundary and surface low in/near the the Texas Panhandle Wednesday afternoon. Ensemble scatter low plots support a low position nearer to the 00Z ECMWF with a 700-500 mb trough depth/timing closer to a 00Z ECMWF/12Z GFS blend. ...Upper trough over the Northern Plains/Midwest Tues... ...Surface cold front crossing the Midwest... ...Initial surface low track through the Upper Mississippi Valley into the Great Lakes Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend, led by the 12Z ECMWF Confidence: Above average ...19Z update... No significant changes were noted the 12Z ECMWF/UKMET/CMC compared to their previous 00Z cycles. ...previous discussion follows... Minor differences remain with this system as a shortwave moves through a broader upper trough covering south-central Canada. The 12Z GFS remains a bit faster while the 12Z NAM is north of the remaining model consensus, though the difference is relatively minor. The 00Z ECMWF appears to be well placed with respect to the middle of the deterministic/ensemble spread. As mid-level height falls overspread the north-central U.S. Tuesday, there is reasonable agreement with the timing and related cold front. A general model blend is recommended to represent the middle of these relative small scale differences. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Otto