Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 230 AM EDT Sun Oct 27 2019 Valid Oct 27/0000 UTC thru Oct 30/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Trough/closed low currently over the OH Valley... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average The latest model guidance shows the upper trough and associated low center over the OH Valley crossing through the lower Great region early Sunday. The energy though will be encountering increasingly confluent downstream flow aloft and the system will weaken substantially late Sunday as it reaches the Northeast. As the attendant cold front reaches the East Coast, the original low center will dampen out in favor of a new area of cyclogenesis near southern New England. This low center will move east and offshore Monday as the remnant energy aloft shifts east toward the western Atlantic and continues to weaken. All of the models are in good agreement now with the details of the mass field evolution, and so a general model blend will be preferred. ...Deep trough digging across the Intermountain West/Plains... ...Closed low evolution over the Four Corners by Wednesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z UKMET/ECMWF Confidence: Above average A strong deep layer ridge over the Gulf of AK this weekend will shift toward northwest Canada early next week which will allow shortwave energy to dig south across southwest Canada and then into Intermountain West and High Plains through the period, leading to the development of a deep longwave trough over the Intermountain West and Plains by Tuesday. As additional energy digs into the backside of the trough on Wednesday, there should be a closed low evolution that settles down toward the Four Corners region. Gradually the 00Z NAM becomes a bit stronger than all of the global models as the closed low evolution takes shape. And by the end of the period, the 00Z GFS becomes the most progressive solution in pivoting the energy farther east across CO, whereas the remaining guidance has the closed low over UT. The better model clustering resides with the 00Z non-NCEP guidance, led especially by the UKMET and ECMWF. So, a blend of the UKMET and ECMWF will be preferred which is strongly supported by the latest GEFS mean and ECENS mean as well. ...Shortwave/clipper low over MT/ND by Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average As the highly amplified deep layer flow pattern evolves across North America early next week, the guidance favors a vigorous shortwave/jet-streak diving southeast toward the northern High Plains on Monday which will drive a clipper low and reinforcing cold front southeast across MT/ND. The models are in good agreement with this feature, so a general model blend will be preferred. ...Surface cold front over the lower/mid MS Valley by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 00Z GFS/ECMWF Confidence: Slightly above average As the deep longwave trough ejects out over the Plains Sunday and Monday, a cold front will settle well south and east, and will be approaching the lower/middle MS Valley region late Monday and Tuesday. Some increase in model spread with the timing of the front and the details of a wave of low pressure riding northeast up along it is seen by early Tuesday. Most notably, the 00Z UKMET tends to be the slowest solution with the boundary as it crosses the MS Valley and approaches the OH Valley. With respect to the frontal wave, the 00Z NAM is most progressive with it. In general, the 00Z GFS and 00Z ECMWF tend to cluster together rather well and have favorable support from their respective ensemble suites, so a blend of the GFS and ECMWF will be preferred for now. ...Potential disturbance in the Gulf of Mexico early next week... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-UKMET blend Confidence: Average There is currently an area of disturbed weather south of Cuba which some of the models track around the western side of the subtropical Atlantic ridge and into the Gulf of Mexico. The models are in sufficiently good enough agreement with the 00Z cycle to support a general model blend. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Orrison