Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1208 AM EDT Mon Jul 02 2018 Valid Jul 02/0000 UTC thru Jul 05/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z model evaluation including preferences and forecast confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Upper trough advancing from the upper Mississippi Valley today into Ontario tonight with accompanying cold front... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The strong mid-level low is maturing as it exits the Great Lakes tonight with good model agreement to support general model blend at above average confidence. ...Westward moving upper circulation along the Gulf Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average A compact upper-level low with excellent outflow bands exists along the eastern Gulf of Mexico coast. The 00z NAM was a bit stronger resolving the wave but also becomes a shade more progressive toward the West through the beginning of the week, but has trended toward the remaining deterministic guidance as well as the bulk of ensemble members. Eventually the 12z ECMWF/UKMET support a stronger wave followed by the 12z CMC and the 00z GFS, which are more in line in shape/timing progressing toward TX by Wed. As such a general model blend can be supported at above average confidence. ...Upper low approaching the southeastern U.S. coast by mid-week... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average The next TUTT cell is translating west under the strong US ridge into FL by Wed. Here the 00z GFS and 12z ECMWF/CMC are strongest/slightly deeper. However, the 00z NAM and 12z UKMET are well in line with shape of the wave as well as timing to have slightly above average confidence in a general model blend. ...Upper low/trough taking shape over Canadian Rockies/Pacific Northwest Mon/Tues...lifting across Northern Plains/S Canadian Prairies into Wed/Thurs. Surface wave(s) along Northern Plains frontal zone. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~ Preference: 00z NAM and 12z UKMET/ECMWF Confidence: Slightly below average Shortwave energy currently crossing into SW Canada sinks south into the Pacific Northwest to take up residence at the base of the larger scale highly positive tilt trough extending from western Hudson Bay. This setup will favor a more progressive amplification of the leading height falls as presented by the 12z ECMWF/UKMET and now the 00z NAM. The 00z GFS and 12z CMC are slow and present a more southern digging leading to a slower ejection of the consolidating closed low by Wed into Thurs (even the GFS is not closed by early Wed, back in N MT). This obviously delays the timing of the surface wave ejecting along the stationary front from the N WY mountains across the Dakotas into Ontario. While the 00z GFS still may not be fully preferred there is a slow trending toward the ECMWF/UKMET. Given the larger global to synoptic scale setup, will favor the progressive evolution of the 00z NAM and 12z UKMET/ECMWF in the blend. Confidence is slightly below average as continuity is not strong AND the system is still entering the deeper data network, with large model spreads as the result. ...Shortwave reaching Canadian West Coast and becoming closed low off US West Coast by late Wed/Thurs... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average Downstream evolution will play a role in the evolution of the closed low off the Pacific coast by Wed/Thursday, so the CMC/GFS are starting of with this handicap. While the CMC and GFS are a bit less defined with the internal shortwave features, the overall shape and placement are fairly well aligned with the mean ensemble suite presented well by the UKMET/ECMWF. The NAM which had been favoring a stronger compact wave initially leading to an eastward bias, but the 00z run tempered this enough to draw toward the growing consensus. The NAM is a bit deeper, like the UKMET, but combine/offset with the weaker CMC/GFS...it appears a general model blend will work within the ensemble suite. With moderate spread and only recent better alignment, confidence is average in this general model blend at this point. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina