Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 231 PM EDT Wed Oct 09 2019 Valid Oct 09/1200 UTC thru Oct 13/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 09/12Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...East Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Any of the operational models Confidence: Above Average A stacked, closed low forming the lower part of a Rex Block will linger with rain over New England before being prodded along by the upstream central U.S. cyclone. The 12Z GFS trended more in line with the other operational models, making for a strong consensus and the ability to use any of the operational models for this system through Day 3. ...Central U.S. Mid-Latitude Cyclone... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Any of the operational models, dropping the GFS after 12/00Z Confidence: Above Average A very deep, 2 to 3 standard deviation trough, will spin up into a large scale cyclone with low pressure tracking from Colorado toward northern Minnesota during the maturing phase, and then lingering in place over Minnesota while a shortwave ridge builds over the top in Canada. Potentially record-breaking October snowfall is possible in parts of the Plains, along with strong winds. The models are in very good agreement with this large scale storm within the upper air network. The *best* consensus clusters around the ECMWF Ensemble Mean, and so would include most of the operational models through Day 3. The exception is the GFS which tends to change shape on Day 3, with energy rotating around and dragging the mature cyclone toward the Great Lakes somewhat unrealistically. ...West Coast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 12Z NAM / ECMWF / Canadian Confidence: Average A complicated merger of two streams around 145 degrees west leads eventually to a more consolidated open trough approaching the west coast by Day 3. Some solutions split the energy again, with emphasis on a southern stream trough anchored off California, and a low amplitude northern stream wave punching into the Northwest. We prefer solutions that are closer to the ECMWF Mean, given its handling of the North American pattern as a whole, and based on synoptic reasoning involving differential advection over the Pacific. The operational ECMWF may be a bit too slow and consolidated, and the NAM a bit too fast, but a blend of the two gets close to the EC Mean, and is a decent representation of consensus. One could throw the 12Z Canadian in there for good measure. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Burke