Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1212 PM EST Sat Mar 10 2018 Valid Mar 10/1200 UTC thru Mar 14/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS evaluation with preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Surface low weakening in the vicinity of New Brunswick and Nova Scoita tonight... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The models show similarly with this system. ...Shortwave(s) dropping southeastward across the Plains today and Mississippi valley on Sunday... ...Surface low tracking across the Gulf Coast States on Sunday with redevelopment off of the Southeast coast Sunday night before tracking north-northeastward on Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non 00Z CMC blend Confidence: Below average Significant model spread and poor run to run continuity remains regarding the main shortwave trough axis and mid-level vorticity max as it reaches the Southeast. The 12Z GFS is toward the northern side of the model spread and 00Z CMC the far southern side valid 12Z/12. A middle ground is preferred here. As the vorticity max continues eastward toward the Mid-Atlantic or Southeast coastline, a surface low is expected to develop and intensify in the western Atlantic. There are still differences with the latest deterministic guidance, but the 00Z CMC appears to be somewhat of an outlier with its surface low lying on the far southern side of the ensemble guidance and south of the latest deterministic guidance. Valid 00Z/13, among the non-00Z CMC models, the 00Z ECMWF is the farthest east, while the 12Z GFS if farthest north. A preferred position would be just west of the agreeable 09Z SREF mean, 06Z GEFS mean and 00Z ECMWF mean, which is near a 4-way blend of the 12Z NAM, 12Z GFS, 00Z ECMWF and 00Z UKMET. Thinking that the 00Z ECMWF may be too weak given recent deterministic trends. This preference continues through 00Z/14 with models trading places with which one is closest to the coast or farther north. Therefore, a 4-way blend will be the preference, excluding the 00Z CMC. Just to reiterate, the ensemble spread and poor run to run consistency lowers confidence with this storm. ...Closed mid-level low reaching the Great Lakes Monday night... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 00Z UKMET blend Confidence: Average Differences are not too large here, but the 00Z UKMET is more amplified with the southeast side of its digging 500 mb low across the Great Lakes through Monday. The 00Z UKMET is a near outlier regarding spaghetti plots of over 90 ensemble members representing the ECMWF, GEFS and CMC ensembles. Outside of this difference, the models are reasonably similar to one another here. ...Low amplitude shortwave approaching California from the west later today... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 00Z CMC blend Confidence: Above average Despite some minor differences, models have converged on a similar solution here. The 00Z CMC, however, is a bit slower at the surface and weaker aloft with the shortwave. Therefore, a non 00Z CMC blend is recommended with this system. ...Large closed low off of the West Coast Monday night... ...Surface cyclone strengthening off of the Pacific Northwest coast Monday night... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/00Z ECMWF/00Z UKMET blend Confidence: Average The ensemble scatter low plots support a 12Z GFS/00Z ECMWF/00Z UKMET blend with surface low forecast to develop near 40N, between 300 and 400 miles west of the northern California coast Monday evening. The 12Z NAM appears a bit too aggressive and eastward with the formation of a closed low, embedded within the larger scale closed low off of the West Coast Monday night. The 00Z CMC is a close second option to the GFS/ECMWF/UKMET preference. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto