Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 141 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 Model Evaluation with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *** Note that the 12Z UKMET was not available for the final update *** ...Digging trough over the Great Basin/Southwest today and ejecting east toward the southern Plains by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of the 12Z GFS/12Z ECMWF/12Z CMC 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/12Z ECMWF/12Z CMC 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. However, a quicker trend in the 12Z CMC places it near the timing of the 12Z ECMWF. Of the preferred 12Z GFS/ECMWF/CMC, the 12Z GFS is a little faster than the 12Z ECMWF/CMC with a blended approach looking best at this time. ...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 12Z ECMWF 12Z CMC as a secondary preference 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 12Z ECMWF given it is considered reasonable with all surrounding synoptic scale features. The 12Z CMC can be considered a second option for this system. ...Shortwave crossing British Columbia Monday night... ...Energy dropping southeast across the northern Rockies Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z ECMWF/NAM/CMC blend Confidence: Slightly below average Uncertainty has decreased compared to Saturday 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 12Z ECMWF, 12Z CMC and 12Z NAM, a NAM/ECMWF/CMC 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/12Z ECMWF/12Z CMC 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