Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 258 AM EDT Thu Apr 11 2019 Valid Apr 11/0000 UTC thru Apr 14/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z NAM/GFS Evaluation with Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep Plains Cyclone through Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General Model Blend (least weight on 12Z CMC) Confidence: Above average ...07Z update... No significant changes were noted in the 00Z ECMWF/UKMET/CMC relative to their previous 12Z cycles. ...previous discussion below... Only minor differences exist with this system regarding strength and timing but the 12Z CMC stands out with a displaced 850 mb low relative to the remaining model consensus. Therefore, a general model blend will work just fine for this system, but little weight on the CMC is preferred. ...Pair of Northern Pacific Shortwaves amplifying into the Southwest through Friday, with eventual cyclogenesis in Texas on Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/00Z ECMWF blend Confidence: Slightly above average ...07Z update... Regarding the upper trough reaching the Southern Plains, the 00Z UKMET slowed down while the 00Z CMC sped up. The 00Z ECMWF looks more reasonable with a less potent shortwave reaching the Southwest, but it did slow slightly with the upper trough progression toward the east beyond Friday night. Considering the latest guidance, there were no changes to the previous thinking and continued wobbles in timing can be expected. ...previous discussion below... Overall trends in the ensembles since Tuesday's 12Z cycle have been a bit faster with the mid-level trough reaching the Southern Plains on Saturday. The 12Z ECMWF was noted to be a bit slower across the Southwest Friday morning which may be caused by a more compact 500 mb shortwave. The 12Z ECMWF was noted to have a more compact shortwave in the Gulf of Alaska valid 00Z/11 compared to water vapor imagery and this may translate downstream into a slower/more potent mid-level shortwave by 12Z/12. By 12Z/13 (Saturday morning), the 12Z UKMET/CMC stand out the most from the remaining model guidance with a slower 500 mb trough progression with the 12Z GFS slightly ahead of the pack. In general, a 12Z ECMWF/00Z GFS blend is preferred, seeming to lie in the middle of the latest ensemble clustering considering recent trends. ...Low amplitude longwave trough with embedded shortwaves and surface cold front into the Pacific Northwest on Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average ...07Z update... The 00Z UKMET/CMC made adjustments in timing/strength toward the preliminary preference while the 00Z ECMWF reduced its shortwave amplitude on Saturday into Sunday. While minor differences remain, the 00Z UKMET/CMC can now be included as part of the blend with a general model blend preferred for the final preference. ...previous discussion below... The 12Z UKMET was much stronger with an embedded shortwave off of the British Columbia coast Saturday morning while the 12Z CMC was slower with the shortwave. Similar evolution noted in the 12Z ECMWF, 00Z NAM and 00Z GFS matched the center of the relatively tight ensemble clustering across the Northwest from Saturday into Sunday. Overall, differences across the Northwest were relatively minor but enough to rule out the 12Z UKMET/CMC. Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Otto