Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1227 AM EDT Fri May 15 2020 Valid May 15/0000 UTC thru May 18/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Closed low over the Northern Plains and Upper Great Lakes tonight...crossing Northern New England Fri... ...Surface low moving from the Northern Plains tonight into Northern New England Fri... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS, 12Z ECMWF, 12Z CMC blend Confidence: Above average Shortwave energy currently along the Minnesota/Canadian border will quickly skirt eastward across the northern Great Lakes and into the Northeast by Saturday. The model guidance has clustered fairly well on a solution except for some timing issues on day 3 between the slower UKMET and faster NAM 500 shortwave timing. These differences are also manifested at the surface where the NAM is a bit too deep and on the northern end of the model guidance while the UKMET is slower and to the southwest. For these reasons, the WPC preference is for a blend of the other deterministic guidance (00Z GFS, 12Z ECMWF, and 12Z CMC). ....Closed mid level low off the Pacific Northwest today...moving to the Northern Plains Sat and the upper Great Lakes Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average A large closed mid/upper level low is forecast to move from the eastern Pacific toward the Pacific Northwest coast through the period. With the highly amplified pattern, the model guidance shows reasonable agreement with only some minor differences at 500 mb on day 3 noted (faster GFS bias). At the surface a low will approach the coast and then wash out by day 3 as the overall system slows/stalls off the coast. The model guidance is now fairly clustered and a general model blend should suffice through the period. ...Developing long wave trough moving from northern Mexico into central TX Sat...then into the Lower MS Valley Sun... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-12Z NAM blend Confidence: Average Weak shortwave troughing will move across the southern Plains this weekend and gradually takes the slow moving mid level slow into the Lower MS Valley by late in the weekend. The 00Z NAM is the least favored deterministic model, as it is considerably slower with the wave moving into the Lower MS by Sunday compared to the rest of the guidance. The 12Z UKMET does remain on the slower side too but has trended toward the rest of the guidance (CMC/ECMWF/GFS) is picking up the system eastward. As such, will continue to favor a non-00Z NAM blend. ...Low pressure developing near the Bahamas Friday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z GFS/12Z ECMWF/00Z ECMWF mean blend Confidence: Slightly above average\ Weak area of low pressure is forecast to develop off the southern Florida coast Friday and gradually move toward the Bahamas Friday night before turning northward this weekend. Forecast guidance agreement and confidence remains average at best and begins to diverge beyond 48 hours. The 12Z UKMET was a clear outlier, well east of the model consensus and most of the deterministic guidance. Meanwhile, the 00Z NAM is on the western side of the model spread envelope as well as a bit deeper with the low as it tracks to near the NC coast by 84 hours. The rest of the deterministic guidance (12Z CMC, 12Z ECMWF, and 00Z GFS) are reasonably clustered through 3 days as a middle ground consensus. There is also pretty good agreement with the GEFS and ECENS means. As such, the favored blend incorporates the 00Z GFS, 12Z ECMWF, 18Z GEFS, and 12Z ECENS. For more information on this system and potential development, see the latest from the National Hurricane Center. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor