Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 245 PM EDT Sat Jun 16 2018 Valid Jun 16/1200 UTC thru Jun 20/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model evaluation including preferences and forecast confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Oblong closed low in the Columbia/Snake River Valleys, drop to N Great Basin by Sun/Mon before weakening and sliding NE into MT by Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blended through 19/12z 12z GFS/ECMWF blend afterward Confidence: Above average until 19/00z...average thereafter Current Goes WV suite depict an oblong closed low over OR/ID with a well defined eastern lobe shifting northeast into MT and toward central Canada by Sun. The western lobe then drops south and consolidates over the Northern Great Basin Sun into Mon with continued strong model agreement in depth/placement and timing. By late Monday, upstream larger global scale ridging will start to become dominant on the western portion of the continent and start to crush the remaining trof energy and the closed low starts breaking down. During this break down period, it will shift eastward, lead by the UKMET while. The 12z GFS continues to show a bit of northward favor with the internal shortwave features compared to the 12z NAM and 00z ECMWF (though the NAM is much stronger/broader by the end of the period). A slower northeast ejection of TC Bud and kicker wave in the Southwest currently, allows for a stronger consolidation of the upper low toward the SE and is off-balance with the remaining guidance though not wildly enough for this system, at least, to support a general model blend weighted toward the GFS/ECMWF/UKMET. Confidence is above average through Monday before becoming average as models can vary significantly with which internal shortwave to enhance during the breakdown/filling process. 19z update: The UKMET and now the CMC are a bit faster weakening an exiting the remaining low across MT into the Dakotas by 00z Wed with the 12z ECMWF trending a bit this way. This puts the deep NAM on the outer side of the trend and would be even further less favored after 19/00z. A compromise of the 12z GFS/ECWMF may be best late Tuesday and is therefore preference at average confidence. A general model blend will suffice before 19/12z. ...Remnant energy of TC Bud and broad mid-level kicker shortwave...lift along NM/CO shearing into confluent flow in the Dakotas today through late Monday into Tues and associated lee surface waves along frontal boundary into Western Great Lakes... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average Goes WV suite depicts the main shortwave core of TC Bud over NW NM at this time, with a broad cyclonically curved kicker wave over northern Baja California. The deterministic guidance are falling in line with typical biases but with only smaller differences in impacts mainly in timing. The 12z NAM, GFS and 00z UKMET are all quite fast with the remains of Bud lifting into the Dakotas by tomorrow morning (Sun 12z) with the NAM much stronger while the 00z ECMWF trails in SW SD/W Neb at the same time and the 00z CMC even slower. The trailing kicker wave is a bit better timed respectfully, but the CMC/NAM followed by the UKMET. Both systems shear and enter into confluent flow at the trailing edge of a Canadian trof (see section below) and accelerate into the northeast by Tues/Wed. At the surface, lee cyclones emerge off the CO High Plains into the frontal zone that extends into the Western Great Lakes...while there is some small differences in depth and timing, there is no discernible model trend/ensemble support for one solution over another, as such a general model blend could be supported for these waves, though confidence is slightly reduced to slightly above average due to the timing differences and their affects. 19z update: No significant departures or change in thinking with the 12z ECMWF/UKMET/CMC or GEFS solutions to break from initial thinking here. Compact shortwave/occasionally closed upper low across central Canada to Labrador by Tues with trailing trof clipping the Northern Great Lakes Mon/Tues and the Northeast Tues/Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average A compact near closed upper low exist over Boreal Manitoba with a trailing trof back to the eastern side of the NW US closed low. As the eastern lobe from the US closed low sheds into the northern stream, eastward progression of the Canadian low will continue toward Labrador by Tues with trailing trof along the US/Canadian boarder. Shortwaves from the southwesterly flow across the Plains (described in sections above) will enhance the confluence zone in this region and support height falls migrating across the Northern Great Lakes Mon into Tues and eventually in the Northeast by late Tues. The 00z GFS shifted slightly pressing the base of the trof through New England a bit further south than the northern-most ECMWF and 00z NAM. The UKMET supports the GFS, but this does not seem to manifest too much, or negatively toward the surface/low level mass patterns, including the stationary front across the Ohio Valley by 00z Wed (with exception of the CMC). All in all a general model blend can be supported though would remove the CMC on Tuesday over the central MS/Ohio valleys. Confidence is slightly above average. 19z update: No significant departures or change in thinking with the 12z ECMWF/UKMET/CMC or GEFS solutions to break from initial thinking here. ...Broad TUTT Cell and low level easterly tropical wave progressing through Western Gulf with high moisture flux possible surface low in NE Mexico/Southern Plains by Late Mon to Wed... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12z GFS/ECMWF blend Confidence: Below average Goes-16 WV suite denotes a forming broad TUTT cell over the SW Gulf/Bay of Campeche but also a strong convective response along the eastern coast of the Yucatan peninsula associated with a downstream tropical easterly wave. Cycle to cycle ensemble continue to show a fairly uncertain development path for these features and appear highly contingent on the strength of the convective complex to generate (or not) a MCV response. The most convectively responsive model is the 00z CMC which develops a deep compact MCV from the start and responds by lifting northwest toward SE TX by Monday, and with its strength, is able to maintain and reinforce the circulation into the Southern Plains with some enhancement from interaction with exiting shortwave energy from the base of the western trof on Monday and eventually the remains of the deep closed low over the Rockies on Tues into Wed. This leads it to depart from the main clustering of guidance and given the preference for faster solutions in other streams (ie reduce positive feedback interaction) will not favor it currently. Other deep solutions are the 12z NAM which not only develops a strong MCV, it develops a surface through CISK response, that may cycle out of control, particularity with no other supporting typically reliable guidance members. The 00z UKMET is next in depth, but unlike the CMC or NAM shows a more reasonable response producing a further north easterly wave response than the 12z GFS or 00z ECMWF. The ECMWF and GFS continue to show some continuity but the ECMWF may be a bit more suppressed focusing further south into Mexico that the GFS. A compromise that gels well with the ensemble suite would favor a 12z GFS and 00z UKMET/ECMWF blend. However, given the large mass spreads and contingency on convective feedback processes (which in turn leads to large spread in direction/track of the easterly wave) confidence is below average. 19z update: The 12z ECMWF shifted toward a weak surface reflection/inverted trof in the Western Gulf in line with the UKMET/CMC but unlike the UKMET/CMC continues to be more progressive in shifting the TUTT toward the west but the overall stronger initial solution brings the day 2-3 period more in line overall with the GFS. The 12z UKMET as noted is a bit more amplified and like the UKMET shows some CISK feedback toward a very strong convectively aggressive solution toward the Central TX coast Tues-Wed. This shift brings some increased concern with this trend, however, like noted before the NAM was too aggressive for our liking at this point. The CMC remains strong initially and lifts faster than the 00z run into the Southern Plains. All considered a removal of the UKMET from the preference but with the ECMWF shifting north and a bit stronger, the difference is likely offset just a bit. Confidence remains below average. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina