Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1217 PM EST Sun Feb 09 2020 Valid Feb 09/1200 UTC thru Feb 13/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z NAM/GFS Evaluation with Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Digging trough over the Great Basin/Southwest today and ejecting east toward the southern Plains by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS/00Z ECMWF Confidence: Slightly above average The ensemble guidance has been fairly consistent over their past 3 12/00Z cycles, with perhaps a subtle nudge to be faster with the closed low progressing across the Southwest. The preference is to be somewhere close to the latest GEFS/ECMWF means which are best represented by a 12Z GFS/00Z ECMWF blend. While the GFS has trended slower from its previously faster solutions, the 12Z NAM has done the opposite and trended faster from its previously slower solutions and away from the better model clustering. The 00Z UKMET/CMC appear to be slow enough, relative to the latest ensemble means, to exclude them from the preference. ...Northern stream trough crossing the Great Lakes today... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Only minor differences remain with this system such that a general model blend can be used. ...Northern stream trough/front over the Midwest by Tuesday... ...Energy crossing the Great Lakes/Northeast by Wednesday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average There are only minor differences with this system concerning timing and amplitude of the mid-level wave and surface reflection. A general model blend should be suitable regarding this system. ...Quasi-stationary front over the Gulf Coast states by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: nearest to the 00Z ECMWF Confidence: Average There are some latitudinal differences that develop on Tuesday with the frontal placement across the Gulf Coast states. The 12Z GFS looks reasonable upstream with a closed low but has a weaker ridge situated off of the southeastern U.S. which causes the front in the GFS to have the front farther south. Overall, considering the ridge to the south, the upstream closed low over the Southwest and a shortwave/surface low to the north, the preference is to be near the 00Z ECMWF given it is considered reasonable with all surrounding synoptic scale features. ...Shortwave crossing British Columbia Monday night... ...Energy dropping southeast across the northern Rockies Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z ECMWF/12Z NAM blend Confidence: Slightly below average Uncertainty has decreased regarding a shortwave that will advance east across British Columbia Monday night and toward the northern Rockies on Tuesday. Models have converged compared to yesterday but the 12Z GFS has a notable slower timing of the shortwave compared to the remaining deterministic guidance. Given the ensemble means do not support the 12Z GFS and match better to a blend of the 00Z ECMWF and 12Z NAM, a NAM/ECMWF blend is recommended. Large differences remain in the ensemble guidance regarding a downstream surface low on Wednesday in the Upper Midwest, but a 12Z NAM/00Z ECMWF blend is nearest to be best clustering observed in the ensemble guidance at this time. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto