Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 145 PM EST Sun Jan 13 2019 Valid Jan 13/1200 UTC thru Jan 17/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation...with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern Across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend -East Non-GFS - West after 15/12z Confidence: Slightly below average to average in Pacific 19z update: For the eastern side of the continent, the UKMET/ECMWF/CMC all trended a bit faster, flatter making the surface wave a bit north of the GFS/NAM and increasing spread a bit. This reduces some confidence and given the typical fast are slow, and slow are fast, think a split/general model blend remains prudent. As for the West, the lead wave continues to have good agreement and though the NAM/ECMWF may be a bit stronger/wound up and slow to lift and the CMC and UKMET have fallen into line with the GFS/NAM/ECMWF to build overall confidence for this wave. The second, elongated wave that has been the largest uncertainty, has seen a marked improvement. This is driven by a slower, less amplified ECMWF/CMC trending a bit more compact and north in the base of the feature, looking similar to the NAM, with the UKMET/CMC a bit more compact while the ECMWF is weaker. This leads to some small timing/increase of QPF for the slower solutions. This matches initial thinking near the 06z GEFS, and questions inclusion of the GFS which is fast, typical of negative bias, especially in a weakening feature. Given the GFS is fast with the main/upstream strong wave, think a non-GFS blend will work after 15/12z with an increase in confidence to slightly below average to average. ---Prior Discussion--- The east coast system will be shifting away from the coast later this evening with fairly good agreement after the surface low establishes off the coast, as there remains some east to west variance in the precise cyclopedias, but fairly minor as any solution is along a consistent axis/placement. As the system slides away the lingering trough over the TN Valley will also quickly shift eastward providing a broad area of westerly/northwesterly flow in the eastern half of the US. A broad vortex develops north of Hudson Bay but in a very stable formation with peripheral shortwaves, including one clipping the northern Great Lakes by late Tues into Wed. Here the ECMWF/UKMET are a shade north and less amplified than the CMC or 12z NAM/GFS but still for day 3 there is strong agreement to further support a general model blend East of the Rockies at above average confidence. For all the agreement East, the Pacific region continues to show volatility and high guidance variation, especially after the initial system breaks down entering California on Tuesday. While, this elongated closed low and moisture plume into Central and Southern CA is agreed upon, the upstream timing/depth and orientation play a significant role thereafter. The 00z ECMWF/CMC are uncharacteristically fast and that is due to the eastern side of a larger central Pacific vortex shedding less energy eastward which becomes fast and highly elongated. The CMC further breaks from the ECMWF with a strong vortex north of 50N which is only marginally supported by the NAM. So will ignore the CMC. The 00z ECMWF while supported by a large chunk of the ECENS members, it is on the faster, southern side of the suite...and the ECENS mean is much closer to the slower/northward solutions presented best by the GEFS mean. The NAM is slow and deeper with this wave clipping northern CA, though the 12z GFS picked up some pace and shifted faster into N CA further separating from bulk of ensemble members. At least the GEFS presses a bit further south and shows the most similarity to the overall trends over the last 3-4 ensemble cycles, giving it the most central potion/shape. The 00z UKMET is somewhere in between in placement of the base of this trof, but typical of its negative bias, it is very compact and fast. All considered, will be shifting to the ECENS/GEFS mean solution for this wave, though with well below average confidence. Quick on the heels of this weaker/stretched out wave, is the core of the larger scale vortex, producing a very strong, very broad surface cyclone, timing of this wave is fairly similar, though the UKMET/CMC remain well displaced. The 12z GFS shifting faster with the initial wave into N CA, allows for a more northward shift of this main deep cyclone, very close to the GEFS mean and 12z NAM and a bit NW of the stronger ECMWF. Thinking the GFS/NAM are likely a bit too fast with this system and the ECMWF is likely too slow. So best to maintain the strength of the a 12z GFS/NAM and 00z ECMWF solutions but shift the centers/timing toward a middle ground or between ECENS mean and GEFS mean locations. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina