Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 134 PM EST Thu Jan 10 2019 Valid Jan 10/1200 UTC thru Jan 14/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Southern Plains to East Coast System... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend weighted heavier toward ECMWF Confidence: Average to slightly above average 19z update: The 12z UKMET showed little change though is a bit faster than the 00z run, further separating from the other guidance and even outpacing the fast 12z NAM as well. The 12z CMC continues to be most concentric through the OH/TN Valleys but is starting to stretch/languish further west with SW angling of northern stream shortwave feature. The 12z ECMWF evolves extremely similar to the 00z run but has slowed a few hours relatively and seems to be the slows advancing the surface low and coastal development by Sun. All in all, will continue to favor the ECMWF highest in a general model blend, with reduced weighting toward the UKMET as the overall spread in timing increases as the upper level pattern flattens by Sun. Confidence remains the same. ---PRIOR DISCUSSION--- A growing consensus has been building and seems to come to a stronger overall agreement with the consolidation of the wave exiting out of the Southern Plains into the Mississippi River Valley by Friday. Now with the vast majority of energy/moisture elements fall in the RAOB/CONUS domain, the GFS which had been a southern outlier followed the 06z GEFS mean trend and has made a sizable shift toward the ECMWF/CMC and NAM solution with the surface wave and overall warm conveyor structure across the Lower MO to Ohio Valleys into the early weekend. Small adjustments have tightened the deformation zone on the western branch of the warm conveyor given slightly stronger northern stream amplification over the last few cycles. This is most dramatically presented by the 12z NAM/00z UKMET with enhanced QPF in the comma head. Given the longer time trend toward a flatter more zonal mid-level flow pattern after the main wave passes...this may be correct but a bit too drastic at this point, so still favoring a more ECMWF/CMC solution for this portion of the system. As the system migrates east, the 12z GFS shift north, allows for this flatter/progressive solution to develop the coastal low further off the coast similar to the 00z ECMWF and 12Z NAM, with less wrap back QPF into the lower Mid-Atlantic. But overall, more traditional model biases in timing, depth, placement are emerging suggesting a middle ground between the 00z ECMWF/CMC and 12z GFS in a general model blend. Confidence continues to slowly increase to slightly above average in the synoptic sense, but impacting sensible weather in the mesoscale will be vastly important and keep overall confidence lower given the run to run spatial/magnitude variations...so average to slightly above average. ...Pacific Coast/Southwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12z GFS/ECMWF blend Confidence: Average 19z update: The 12z ECMWF trended a bit stronger with the surface wave/shortwave amplified in the diffluent flow lifting northward, this stalls it a bit compared to the 00z run/12z GFS, but weakens in the shearing environment well enough to remain close, even outpace the GFS by Sat. The CMC/UKMET both trended faster as well and match very close to the 12z NAM, lifting them north, but like the 00z this delay north lends to a binary interaction that swings the next wave southward but at reduced distance from the 12z GFS/ECMWF agreement. As such will keep with the initial preference of GFS/ECMWF at average confidence. ---PRIOR DISCUSSION--- GOES-West WV depicts occluded but still strong closed low dropping south at 45N145W with a strong subtropical jet and enhancing wave to its southeast along 140W. The melding of these systems in advance of the strengthening blocking across the Great Basin, continues to lead to moderate spread though a common solution appears to be emerging in the ensemble suite. The main issue is the elongated southern stream wave and the strength of the diffluence on the northeast side of the wave. Uncharacteristically, the ECMWF has been fast and generally flatter with this portion of the wave spurring a weaker, northward surface inflection (relative to other guidance) that shifts toward Vancouver Island by Sat, while the remaining trof energy digs south of the blocking ridge into S CA with ample moisture advection. The ECWMF has trended slower and therefore southward over the last few runs, but the GFS and GEFS has trended quickly toward this solution (as well as the FV3-GFS)...hence the tightening of the overall ensemble suite. The 12z NAM/00z UKMET and 00z CMC having greater diffluence/divergence spur stronger cyclogenesis and given the orientation of the next digging trof stalls near the 40N130W benchmark leading the next system entering the picture late Sun to be well south of the ensemble suite (eventually the CMC breaks away trending toward the GFS/ECMWF having been slightly weaker than the NAM/UKMET). So even though the UKMET/NAM shift the warm conveyor/moisture surge into the Central and Southern CA coast Sat in a similar vein as the GFS/ECMWF...will favor the GFS/ECMWF overall to handle the mass fields upstream setting the stage better at the end of the forecast period (for offshore marine impacts). While the spread is reduced overall in the deterministic guidance, confidence is increased to average in the GFS/ECMWF blend. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina