Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 237 AM EDT Thu Jun 25 2020 Valid Jun 25/0000 UTC thru Jun 28/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z Model Evaluation Including Preferences and Forecast Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Closed low over Ontario/Quebec Trough crossing the eastern U.S. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/00Z CMC/00Z ECMWF blend Confidence: Slightly above average The 00Z NAM/GFS are close to the consensus with the mid level closed low as it tracks from eastern Ontario into western Quebec, before slowing down and spinning over central Quebec through 28/12Z. However, the 00Z NAM appear to be too fast with its surface low crossing northern ME (as it the 00Z UKMET, which sped up with the surface and mid level systems here), while the 00Z GFS/00Z ECMWF show better clustering with the 12Z ECMWF ensemble mean (and the front that moves across the East Coast late in the period). The faster 00Z UKMET and 00Z NAM solutions were dropped from the consensus, leaving a fairly tight cluster comprised of the 00Z GFS/00Z CMC/00Z ECMWF). The forecast confidence remains slightly above average, as the abovementioned cluster has the support of ensemble means. Short wave crossing the Pacific Northwest and Plains/Midwest Long wave trough digging into the Southwest ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Above average For the short wave energy tracking from the Pacific Northwest into the Northern Plains, the 00Z NAM/GFS are close to the consensus taking it across SD into IA/IL, as well as the surface low moving across Ontario. These solutions are close to their ensemble means, as well as the 12Z ECMWF Ensemble mean. Given the tight clustering, a general model blend is preferred. For the positively tilted long wave trough crossing CA after 26/00Z, the 00Z CMC slowed its timing with the mid level system, and now is part of the tightly clustered solution as the mid level system reaches the Southwest states by 28/12Z. Strong shortwave trough over the Pacific Northwest this weekend ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average The 00Z NAM/GFS are close to the consensus taking short wave energy from the Gulf of AK across the British Columbia coast after 27/00Z. Additional mid level energy dropping into the short wave position over British Columbia/Alberta causes the system to closed off over the Pacific Northwest toward the end of the period. By that time, the 00Z NAM/GFS are a bit faster than the consensus, but there is more spread in general throughout the model solutions. However, this cluster is not far from the 12Z ECMWF ensemble mean/00Z GEFS mean, so the slightly faster solutions are not too fast not to include in a general model blend. Given the spread, though, forecast confidence is average. Lower MS Valley and Gulf Coast states ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average Though the 00Z GFS is a bit stronger with the short wave energy in the mid level flow across the region, it does have some support from the 00Z UKMET. Overall, there is fairly good clustering in the mid level flow (outside of weak impulses in the mid level flow that regional/global models cannot yet resolve) as heights fall across the Lower MS Valley and Gulf Coast states. Based on this, a general model blend is preferred, with slightly above average confidence. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Hayes