Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 129 PM EST Wed Feb 05 2020 Valid Feb 05/1200 UTC thru Feb 09/0000 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 12Z Model Evaluation with Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ ...Evolving full latitude trough over the Central US through Thu... ...Surface wave(s) developing over the Lower MS Valley...moving into the interior Mid Atlantic late ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~ Preference: General model blend Confidence: Average to slightly above average 19z update: There is continued strengthening congruence, even in the timing/spacing of the two waves interacting through the Gulf and into the Southeast/Mid-Atlantic. The UKMET appears to have slowed sufficiently with less over deepening as well. The CMC flopped across the timing to become a faster overall solution, near the UKMET but again not terribly out of tolerance. The ECMWF trended a tad faster too, so overall a general model blend can be afforded. Yet, there remains moderate smaller scale differences, to have some continued reduced confidence, but it is much improved overall. ---Prior Discussion--- GOES-East WV depicts full latitude trough continuing to advancing into the far Southern Plains, Northern Mexico. The other main shortwave energy is seen across MT starting its southward track to interact with the base (with associated jet streak) late Thursday into Fri. The base shortwave/height-falls advancing today, will support a deepening surface wave across the Lower MS valley that rides northeast along the stationary frontal zone through the South into eastern KY by early Thursday. Overall model guidance appears to be getting much stronger in agreement with this surface wave. However, there remains uncertainty with the timing/spacing between the upstream shortwave coming out of the Rockies rounding the base on Thursday and supporting a secondary surface low that emerges from the Central Gulf and lifts along the spine/just east of the S Appalachians by Fri morning. The UKMET remains quite strong, greater negative tilt rounding the base with greater moisture flux northward, even outpacing the 12z NAM/GFS, which continue to trend a tad slower. The 00z ECMWF/ECENS mean suggest a slightly faster pace, so there is increasing agreement in timing. Though like the UKMET being too fast, the CMC is generally much weaker given the spacing between the lead wave and upstream shortwave is most distant. All considered a ECMWF dominant blend with the 12z NAM/GFS and the GEFS/ECENS blend is preferred at average to slightly below average confidence. ...Elongated shortwave (pair of shortwaves) over-topping ridge in BC on Thurs/Fri drops into Mid-MS Valley Sat supporting a weak surface wave... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: Non-NAM blend Confidence: Average to slightly above average 19z update: The 12z UKMET backed off the over-amplified wave through the MO Valley, but continues to outpace the rest of the guidance through the Ohio Valley by 84hrs, if just slightly so over the GFS. The ECMWF/CMC were a bit slower as to be expected, relative to the GFS/UKMET...but not too significantly to dismiss either camp. As such the NAM is the sole out of tolerance solution to support a non-NAM blend at slightly above average confidence. ---Prior Discussion--- Strong flow over-topping a broad but dominant Eastern Pacific/West Coast Ridge will stay in place through the remainder of the week. The associated jet support an elongated shortwave energy that slides into the Central Plains by late Thursday into Friday, with little fanfare in the wake of the exiting long wave trof. However, the tail end of the jet/slightly enhanced shortwave shears through the Rockies on Friday, eventually slightly amplifying across the Lower MO River Valley Sat morning. Here, the bias of the NAM as well as the UKMET suggest greatest amplification increasing moisture flux off the western Gulf allowing for increased QPF through the Lower MS valley. Ensembles and operational solutions from the ECMWF/GFS and CMC suggest a bulk of flatter solutions and therefore less low level response. Given the wave(s) position between stronger systems, there is increased likelihood for a flatter solution and therefore will favor a 12z GFS and 00z ECMWF/CMC blend for these features with confidence enhanced by the ensembles. ...Approaching rapidly deepening cyclone toward Pacific NW by Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~ Preference: Non-NAM blend Confidence: Slightly above average 19z update: The 12z UKMET shifted much faster, the 12z ECMWF made small adjustments toward the GFS and the CMC slowed enough to be within tolerance as well providing an increased overall confidence toward a non-NAM blend at slightly above average. ---Prior Discussion--- A strong closed low will advance through the Aleutian islands and AK peninsula by Fri, with strong shortwave energy digging into the Western Gulf of AK... moderate longwave ridging remains even after the entrance to the synoptic jet exits (relatively) with the shortwave described in paragraph above. This allows for a progressive but rapidly evolving shortwave that approaches BC/Vancouver Island toward the start of the weekend. The 12z GFS is quite open with the wave with less of a compact inner core/vertically stacked low by 00z Sat. This is supported by the CMC. While the 00z UKMET and 12z NAM are very strong/compact, this slows both solutions relative to the ensemble suite and is in line with typical negative bias of over amplification by the end of day 3. The ECMWF is more central and sensible relative to both camps with a majority of the ECENS solutions a bit slower. This favors the ECMWF overall by traditional verification within the overall suite and the evolution looks quite realistic given the Rex Anticyclone development across AK itself. As the wave enters the NW, the GFS/CMC slow to adjust closer to the ECMWF. So all in all, a ECMWF dominant blend is preferred with some inclusion of the faster GFS/GEFS and slower ECENS mean to account for the modest uncertainty. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Gallina