Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 137 AM EST Tue Nov 05 2019 Valid Nov 05/0000 UTC thru Nov 08/1200 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 through 08.12Z ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend through 07.18z 00z GEFS/GFS/ECMWF and 12z ECENS mean blend Confidence: Above average thru 07.18z Below average thereafter 07z update: The 00z ECMWF trended slower with the shortwave emerging from the Southwest, pressing the frontal zone southeastward; allowing for the northern stream to trend faster, and increase phasing in a similar vain to the 00z GFS. As such the developing coastal low is much further north though still not as far northeast as the GFS. The UKMET further disconnected the tropical moisture connection off the Atlantic and so breaks down the cyclogenesis even further to the east and is no longer within the realm of the ensemble suite. The 00z CMC stayed most consistent but also starting alluding toward a northward shift relative to the prior run. All this leads to further uncertainty, especially since the 12z GEFS showed greater within ensemble agreement and is a split between the new ECMWF and 00z GFS. Given all the guidance has been varying from run to run, and the better verifying guidance is starting to agree further north, will adjust and support a change toward a 00z GEFS/ECWMF/GFS blend with some 12z ECENS mean to handle some of the other uncertainty and keep some blend of continuity within the preference. Confidence is below average after 07.18z ---Prior Discussion--- Deterministic guidance and ensemble suite continue to be in very strong agreement with the CONUS weather pattern through much of the short-range forecast period. However, model spread significantly increases on the latter Day 3 period particularly with the evolution of a coastal surface low in New England very late Thursday into Friday morning. Evolutionary differences appear to be driven in a typical fashion by a weakening/sheared closed low emerging out of the Southwest, its influence/interaction with Gulf moisture to develop convection, with the said convection feeding back upscale to the upper level subtropical jet streak and its influence with the polar jet stream. As such, model spread is actually quite large at the day 3 period across the Northeast, as the much of the current system is in the data assimilation poor region in the cold current region of the Subtropical Northeast Pacific and as a byproduct, the convection has yet to develop providing strength/upscale feed-back to the synoptic system. Through day 2 into early day 3, the guidance is very well agreed upon, particularly in the axis, spacing of the frontal zone across the central/southern Plains into the Ohio Valley, it is the timing of convective initiation and the placement of the upscale ascent/jet enhancement relative the timing of the northern stream shortwave (phased or just offset) that leads to the variation. The 00z NAM and 12z CMC are most aggressive with the convective development pressing it faster into the Ohio Valley and ahead of the northern stream shortwave bring the 150+kt 250mb jet nearly 6-12hrs prior to other guidance. This allows for greater amplification and more compact downstream evolution through the New York Bight and eventually the deepest surface evolution by 12z Friday. The placement, timing is supported by the 12z ECWMF but, this may be a bit off, given the ECMWF is uncharacteristically the fastest bringing the sheared shortwave out of the Southwest, but is also the slowest with the northern stream shortwave, so the upper level jet enhancement is delayed. Ensemble trends would support this evolution a bit more than the highly aggressive CMC/NAM. The 00z GFS, is very fast exiting the prior shortwave trof and is uncharacteristically slow bringing the shortwave out of the Southwest, this eventually leads to the most phased evolution across the Ohio Valley, but also well north of the other solutions, including the bulk of GEFS members, making it less desirable to include in any blend. The 12z UKMET shows a less amplified solution overall, likely as it is most disconnected in the low level stream confluence, particularly the return Atlantic stream lifting north along the East Coast, as such the surface evolution is much weaker but in decent placement compared to the ECENS mean/GEFS mean. So overall, a general model blend is supported across day 2 and through the Central Plains/Mid-MS valley... but a ECMWF, ECENS mean blend with low incorporation of the GEFS, UKMET is preferred thereafter but at much reduced confidence (Average to slightly above average). Model trends at www.wpc.noaa.gov/html/model2.html 500 mb forecasts at www.wpc.noaa.gov/h5pref/h5pref.shtml Gallina