Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 237 AM EDT Thu Jul 30 2020 Valid Jul 30/0000 UTC thru Aug 02/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Mid-upper level troughing over the Northeast to the Ohio Valley and Mid Atlantic... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of UKMET/NAM/ECMWF Confidence: Average The models indicate a deep layer trough drifts east across New England, with fairly good clustering of solutions, allowing a consensus based approach to be used. Differences exist as the wavy front in the Ohio Valley moves east across the Appalachians across the Mid Atlantic states. The GFS lacks waves on the front noted in the NAM/UKMET/Canadian/ECMWF, so the GFS is least preferred. The NAM/ECMWF/UKMET/Canadian have timing/phasing differences. A blend of these solutions is preferred to utilize intermediate timing until better agreement develops. ...Energy advancing south from the Plains Thursday to the lower MS Valley Fri and Ohio Valley Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of 00z NAM/12z UKMET/00z ECMWF Confidence: Average Mid-level energy coming out of the Central Plains slowly sags southeastward toward the Ozarks on Friday and amplifies in the larger scale troughing along the MS River Valley through the Great Lakes region by Saturday morning. The models develop low pressure in the lower MS River Valley Fri night to early Sat. The 00z GFS/12z Canadian were faster in the low pressure progression, which are least favored as usually amplifying troughs favor slower moving, more amplified systems. So the preference here is the cluster of the 00z ECMWF/12z UKMET and 00z NAM. The 00z UKMET became a deep, slow outlier so there is more confidence in the 12z UKMET than 00z run. ...Tropical Storm Isaias proximity to FL/ the southeast coast this weekend... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: NHC Advisory Confidence: Refer to NHC products The models have significant differences on the track of Tropical Storm Isaias, with the 12z-00z ECMWF/00z NAM overall a bit closer to the NHC track, with the 00z GFS/12z Canadian global well removed from the official track. the 00z UKMET has a similar track, but slower timing. For the latest information on Tropical Storm Isaias, please see the latest NHC advisory. ...Cold front moving through the north-central U.S. Friday and Saturday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of ECMWF/GFS/NAM Confidence: Average There is relatively good agreement for the trough axis and related cold front impacting the north-central U.S. through Saturday. While minor timing differences are evident, such as the low pressure along the front 00z Sat in different locations among the GFS/CMC/UKMET, the differences are small enough to allow for a general model blend at this time. ...Upper low/trough approaching the Pacific Northwest... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of ECMWF/GFS/NAM Confidence: Average Due to the high amplitude downstream ridge over the interior west, the mid-upper trough over the eastern Pacific will be slow to move east. There are no significant differences noted with this system, with a lead short amplitude progressive 700 mb wave moving north across WA included on day 2. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml This product will terminate August 15, 2020: www.weather.gov/media/notification/pdf2/scn20-58pmdhmd_termination. pdf Petersen