Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1156 PM EST Mon Nov 11 2019 Valid Nov 12/0000 UTC thru Nov 15/1200 UTC ..See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... ...00Z NAM/GFS Evaluation with Preliminary Preferences and Confidence... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Departing East Coast storm system today/tonight... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average No significant differences were noted with this system until after the surface low has exited northward into the Canadian Maritimes. The 12Z UKMET tracks the surface-850 mb low farther inland than the model consensus, but given this difference has little to no impact on the lower 48, a general model blend is preferred. ...Shortwave tracking from the Northwest to the Great Plains for Wednesday and Great Lakes for Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average Good agreement was noted in the deterministic and ensemble guidance regarding this system. However, the 00Z GFS was slightly slower than the remaining consensus, but this difference is small enough to not be a concern when used as part of a general model blend. ...Weakening closed low crossing Mexico and possible interaction with shortwave dropping southward from the Lower Mississippi Valley on Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z ECMWF/UKMET blend Confidence: Slightly below average The 00Z GFS is significantly faster with the closed low crossing Mexico into the Gulf of Mexico, on the fastest edge of the latest ensemble guidance. The remaining deterministic guidance is in good agreement with the remnant closed low/shortwave crossing Mexico/southern Texas on Thursday. Larger differences exist with mid-level vorticity dropping southward (originating from the Gulf of Alaska Tuesday morning) into the central Plains and eventually the Lower Mississippi Valley Thursday night as the 00Z NAM and 12Z CMC are faster starting Thursday morning. Differences with the 00Z GFS regarding the shortwave to the south precludes its usability across the Gulf Coast/Lower Mississippi Valley. The 12Z ECMWF/UKMET are in fair agreement and match best to the agreeable ensemble means with the 500 mb vorticity within the trough axis and low level baroclinic boundary in the Gulf and just offshore of the Southeast coast. Blending the 12Z ECMWF/UKMET surface low positions along the frontal boundary are best to align with the middle of the latest ensemble scatter low plots. Confidence is reduced given the complexity and potential interactions of various features downstream and upstream. ...Pair of mid-level shortwaves approaching The West Coast on Thursday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average A relatively weak mid-level shortwave is expected to approach The Oregon/California coastlines early on Thursday while a second shortwave lurks to the north with a likely destination of Washington/British Columbia Thursday night. Despite some minor timing differences of these two features, agreement is good enough to warrant a general model compromise which aligns with the latest ensemble means. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto