Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1105 PM EST Tue Jan 29 2019 Valid Jan 30/0000 UTC thru Feb 02/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation...with Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Overall Pattern across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend West Coast after 01/12z: 18z GEFS/12z ECENS blend Confidence: Above average West Coast: Average to slightly below average The deep cold blast over the Great Lakes and associated closed low quickly shift northeast and exit into Eastern Canada under excellent model agreement. This model agreement also is manifested with the compact but much smaller closed low sliding through the Central and Southern California coast Thursday, keeping well agreed upon through the Desert Southwest on early Friday. Afterward, there is modest spread forming as the wave breaks down into the Southern Plains and intersects with Western Gulf/Bay of Campeche moisture late Friday into Saturday. Typical day 3 biases show up, with the 00z NAM and 12z ECMWF slower to break down and therefore a bit slower; The 00z GFS and UKMET a bit faster. Effects to sensible weather/QPF are fairly mild to keep a general model blend preference. ---West Coast after 01/00z--- In the wake of the compact system, a pattern changing flow regime supports a broad but modestly high amplitude Pacific trof to advance toward the West Coast. By 12z Friday, a eastward translating pivot vort center will advance to Vancouver island while energy at the base will start to amplify towards a closed low by the end of the forecast period. Influences from digging trof out of the Yukon will allow this pivot wave to accelerate across WA/BC by the end of the forecast period. There are some small timing/evolution (ie shape) differences, mainly with the 12z UKMET (fast) and 12z CMC (slow) but allow for increased right entrance dynamics to support outflow for the deepening southern stream wave...or at least more so than the remaining deterministic guidance as well as ensemble suite. It is the base of the trof, that has shown the most significant differences and run to run variance likely due to the potential strength of the dynamic setup. As alluded to, the UKMET is most aggressive and the faster southern stream wave lifts north well west of the growing consensus in the ensembles. The 12z CMC, while slow is also aggressive with the deepening of the closed low and therefore West. The ECENS suite has been very consistent in the overall faster envelope of the trof, and the 12z ECMWF is no exception. However, it did deepen the cyclone on the SE side of the ensemble suite initially alone. However, the 18z GFS/GEFS both shifted toward the ECWMF and ECENS means respectfully...and this trend was carried over to the 00z NAM. The NAM is a bit slower than the ECMWF...and would suspect is still well within the likelihood of most likely outcomes. The 00z GFS faded this trend, favoring a slightly faster southern stream and digging the trof less than the 00z NAM/12z ECMWF eventually closing off the deepening low just north of the 18z GEFS/12z ECENS mean off the NW CA coast...on par with the 12z CMC if just a bit east. As such favoring a blend of the 18z GEFS/12z ECENS mean which would close in position to a 00z GFS/12z ECMWF blend. While the overall pattern seems to be coming into focus, providing confidence; the large spread in sensible weather/QPF position leads to reduced overall confidence to average to slightly below average in this GEFS/ECENS mean 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