Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1117 AM EST Wed Jan 09 2019 Valid Jan 09/1200 UTC thru Jan 13/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Strong Broad Cyclone over Northeast exiting by Fri... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average Guidance including the bulk of ensemble member solutions show remarkable agreement in mass fields to have well above average confidence in a general model blend. There is some small differences entering Saturday as the CMC and GFS fall out of phase in timing with the upstream kicker shortwave out of S Hudson Bay across the Rooftop of ME as it is slow to weaken the system leading it to be slightly slower, while the GFS in typical fashion is weaker and too fast. So would favor shifting toward a 12z NAM, 00z ECMWF/UKMET blend for this wave, though its sensible weather is much less of a factor compared to the initial main system ...Multiple stream shortwaves coalesce in Southern Plains Fri into Sat/Central US Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00z ECMWF/CMC and small weighting of 00z UKMET Confidence: Average The break down of the West Coast trof, fractures the system a bit crossing the Great Basin and Rockies Thursday into Friday. As the mean wave crosses into the High Plains, there are increased differences in strength of internal shortwaves/speed maxima leading to slight evolutionary differences as it consolidates across the Southern Plains into a deeper cyclone. Additionally, northern stream shortwave across the Dakotas will play a role (positive and negative) along with shortwave from the subtropical Pacific including moisture plume. Cycle to cycle ensemble suite tries to come to agreement, but it appears to be bifurcating into GEFS and ECENS members. Here the ECWMF/ECENS mean shows a bit greater run to run continuity but the operational 00z run depicts a more sensible interaction of the internal waves than the 12z GFS/06z GFS-FV3; however it appears slow, typical of bias to the overall mean and other guidance. The 00z UKMET continues to show the deepest solution especially initially (typical of bias), but also is slightly faster than the ECENS mean. The 00z CMC interestingly appears the most middle ground in timing, shape and depth compared to the ensembles and trends, even though there are multiple upstream and downstream issues that give some pause for its inclusion. Still, specifically here though it should have some stronger influence in the preference (though the CMCE is inconsistent/variable). The 12z NAM removed some of the influence of an over amplified northern stream shortwave drawing the overall system and QPF further north than other guidance. While it is dampened, the stronger jet/temp gradient supports a faster solution now especially in the downstream deformation zone in the Great Lakes/Northern Ohio valley, and is not particularly favored overall. The GFS has been slightly faster in the southern stream and reduces the timing to interact with the northern portion of the wave descending out of the Northern Rockies Friday, this leads to a faster and much weaker solution overall emerging out of the Southern Plains into the lower Mississippi River Basin; the 12z GFS trended favorably, shifting a bit further north overall compared to the GEFS mean and members which were less favored. Still, while better, the overall shape, QPF magnitude north is less favored. As such will favor a 00z ECMWF/CMC blend with a lower weighting/inclusion of the 00z UKMET. Confidence in this solution is a bit lower than normal for such a broad wave with modest positional agreement, but the internal wave interactions continue to drive the overall evolution and the run to run and model to model variations of these internal features vary too much to have any more than average overall confidence. ...Deep latitudinal trof along the CA Coast by late Sat and entering Southwest Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-CMC blend Confidence: Slightly below average The Pacific remains highly amplified and by Friday the elongated trof slowly advances eastward with some indication of a pinching point between energy centers near 40N; however the northern portion of the wave sheds more energy south with the timing a jet streak dropping south on the western side of the trof. This helps to lift/kick the base shortwave north and spur surface cyclogenesis. The ECMWF led the trend for a slightly faster, stronger solution further north...and the 12z NAM and GFS followed suit though still not to the same magnitude, suggesting the ECMWF may be a bit too far north/fast which shows up in the ensemble surface low plots. The 00z UKMET favors a stronger compact system and is slow to lift the base energy north and presents the deepest surface wave in advance of the next digging wave reaching 130W by 00z Sun. The 00z CMC being slowest overall does sever the connection leading to a closed low off S CA and more progressive flow driving the northern wave into N Vancouver Island; making it a clear outlier. The digging jet streak/shortwave that entered the base late Fri and Saturday, continue to swing south toward the Southern California Bight. Much like with the lead wave, the ECMWF is uncharacteristically fast possibly drawn by the slower downstream wave and weakness in the ridge in the Southwest. Still, the 12z GFS/NAM and 00z UKMET are slightly slower but show a good agreement to have solid confidence in this direction though ensemble trends suggest they may be a bit too slow too. So will support a non-CMC blend overall through both features in this elongated trof. Large model variations and a less than solid ECMWF/ECENS solution (uncharacteristically fast), leads to slightly below average confidence overall. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina