Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1249 PM EDT Fri Sep 20 2019 Valid Sep 20/1200 UTC thru Sep 24/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS and 00z UKMET/ECMWF blend Confidence: Average The strong southeastern ridge will continue to be stalwart in efforts to deflect approaching larger scale northern shortwave troughs. In the West, a compact closed low in SE ID/N UT will continue to advance northeast but is embedded in a larger scale deep latitude trof with amplifying energy in Canada as well as a jet streak that is starting to slide along the western side of the trof to carve out the trof further south across the Four Corners region by late Sat. This will support multiple surface circulations along the High Plains into Manitoba. The binary interaction internally to the trough continue to lead to the largest spread/uncertainty; however, it is getting better agreed upon through the ensemble suite. The main outliers continue to the 12z NAM which is not too bad with the initial closed low wave ejecting into the plains, but is very strong with the lingering base energy that rolls up and is quite compact/deep rolled up but also fast compared to other guidance. The other main outlier is the 00z CMC which shows very strong northern stream vort energy that leads to a tight/strong binary interaction across the northern Red River, leading to a strong/slow to weaken occluded surface low. The 12z GFS slowed a bit and becomes a bit more compact over the Great Lakes by Day 3 but falls in line with timing of the ECMWF (which may be a bit too compact/deep by 23.12z too, especially relative to the 00z ECENS mean suite). Still, for this wave/deep frontal zone across the Midwest into the Southern Plains, a GFS/ECWMF/UKMET blend remains preferred at average confidence. ....Shortwave Entering West Sunday, and digging to closed low in Great Basin by late Monday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00z ECMWF/CMC and 12z GFS blend (mass) Confidence: Slightly above average (mass) Further upstream, the next shortwave energy continues to remain agreed upon and with still some lingering/slower prior wave, a sharper wavelength ridge builds between to allow for the next wave to stretch north to south and eventually start to close off over the S Great Basin to Lower Colorado River Valley. The NAM being fast with the prior wave, does not block enough to stretch south enough and is not a closed off. The 00z UKMET appears to be a bit too fast, which is a bit in line with its bias, given a weaker downstream ridge axis. Overall, the mass fields support a 12z GFS and 00z ECMWF/CMC blend; however, complications with moisture associated with TC Lorena will lead to large differences in QPF. The 12z GFS, being very strong with Lorena and lifting it through the Sea of Cortez, brings moisture toward the region faster and will be shunted southeast given influences from the lingering tail end of the prior trof. Given the placement and strength of Lorena, it may be onto something, as the other guidance, kills Lorena in favor of TC Mario. The ECMWF, CMC on the other hand, having killed off Lorena, allow for deeper moisture pumping back into the desert SW by the end of Day 3, and therefore suggest greater convective activity ahead of this deepening closed low. At this time, the NHC forecast preference is tilted toward the ECWMF/CMC, but again with the GFS the only deterministic (along with a much weaker NAM), may have a better handle on the current assimilation to the guidance. Confidence in the northern stream evolution is slightly above average, but this uncertainty with QPF is below average. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Gallina