Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1218 PM EDT Wed Jul 11 2018 Valid Jul 11/1200 UTC thru Jul 15/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z model evaluation including preference and forecast confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Model Analysis for the CONUS... Overall Preference: 12Z GFS/00z ECMWF blend General Confidence: Average Goes-WV depicts a subtle speed max/shortwave over-topping the ridge in SW Ontario that will slide down the eastern side of the ridge and with lingering s/w energy will help kick and accelerate Chris northeast, but also leave remaining energy to reconstitute a trof off the Eastern US coast with slow evolution to a weak closed system. The 00z CMC/UKMET are quite aggressive and strong with the closed low eventually digging further south (and east for the UKMET). The 12z NAM while initially deeper with the wave than the mean ensemble suite, unfolds and lifts out toward the northeast. The 00z ECMWF and 12z GFS reside much closer to continuity and ensemble means but this pattern, and in particular the placement of weak surface low(s) along the Gulf Stream is a lower predictability environment...so will hedge toward these more reliable and consistent weak closed low presented by the GFS/ECMWF. A second closed low and associated front, currently moving central Canada and North Dakota,respectfully, is expected to continue eastward over the next couple of days with the tail end aligning with the small but compact shortwave in CO lifting/shearing northeast across the Midwest and Plains, reinforcing the LLJ and frontal forcing. The main difference here appears to be related to the southward sag of the frontal zone and the strength of the ridge over the Ohio valley, which is related to the timing/strength of the CO s/w lifting out... The 12z GFS shifted to a faster/stronger solution lifting out this wave and is on par with the 12z NAM both suppressing the ridge. The 00z UKMET/ECMWF/CMC show a more amplified ridge across the Lower Ohio River valley helping to press the frontal zone further north...though the ECMWF is more in the middle shifting more of the energy out of CO than the UKMET/CMC. Given the CMC/UKMET also have downstream deeper solutions this seems reasonable to reduce the pumped up ridge and shift to a GFS/ECMWF compromise. The parade of troughs out of the Gulf of Alaska continues Fri into Sat; and like the prior, deepens toward a closed low over N Alberta/Sask. by midday Sat with a trailing vorticity center in the weak positive tilt trof crossing the US Pacific Northwest. Here the 12z GFS and NAM are faster with the amplification of this vort center as it deepens the triple point in South Central Canada Sun...though the 12z GFS did trend slower toward the GEFS/ECENS best cluster and the 00z ECMWF. The UKMET and more so the CMC lag this wave even further and in the process deepen it into a very strong compact wave and subsequent surface low in the Lee of the borderland Rockies and pull out into the Canadian Prairies well slow... which leads to the cold front also lagging with stronger forcing for deeper convective response. All in all, the UKMET/CMC are not favored here as well. In totality, a blend of the 12z GFS and 00z ECMWF seem a reasonable solution CONUS wide, with some inclusion of the 12z NAM in the third system (NW in late period). Confidence is average given small variations lead to moderate spread, especially off the east coast. ...Hurricane Chris off the East Coast... Best Proxy to 15z NHC forecast: General model blend Please see the latest NHC products for the official forecast, reasoning, and model track and intensity preferences for Hurricane Chris. The latest deterministic models show very similar track/intensity clustering near the 15z NHC official forecasts...through Newfoundland late Thurs into Fri. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina