Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1258 AM EDT Thu May 07 2020 Valid May 07/0000 UTC thru May 10/1200 UTC ...See NOUS42 KWNO (ADMSDM) for the status of the upper air ingest... 00Z NAM/GFS Evaluation Including Latest Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Short wave tracking from the Northern Rockies across the OH Valley to the Mid Atlantic... ...Strong vortex moving from Ontario into Labrador ...Deepening surface low from the OH Valley to the Northeast... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/12Z ECMWF/12Z ECENS mean blend Confidence: Slightly above average The 00Z NAM/GFS are close to the consensus taking the strong short wave from western MT into MO through 08/12z. After that time, the 00Z NAM shears out the short wave energy in the fast flow over the Mid Atlantic states. The 00Z NAM then takes the surface low from the OH Valley to the northern Mid Atlantic coast more quickly, moving it across Southwest Nova Scotia (much like the 12z UKMET) after 09/12z. By contrast, the 00Z GFS phases the short wave energy the vortex dropping southeast from Ontario, and resulting in a more southwesterly mid level flow ahead of the vortex. The more southwesterly flow allows the surface low to track further west across Downeast ME (much like the much more consistent 12Z ECMWF, but just a bit slower and a touch deeper). The 12Z CMC follows a similar path, though it is quicker with the phasing, allowing its surface low to race ahead of 00Z GFS/12Z ECMWF consensus with the track of low. Obviously, the key to the forecast is going to be just how the short wave over the Northern Rockies this morning phases with the vortex dropping out of Ontario. The better agreement between the 00Z GFS/12Z ECMWF increases confidence for a solution further west (bolstered by the support of the 12Z ECMWF ensemble mean). Forecast confidence has increased a bit because of the agreement, but it is clear that the phasing scenario is not quite locked in yet. ...Shortwave/surface low impacting the northern Rockies and northern Plains Fri/Sat... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS/12Z ECMWF blend Confidence: Slightly below average The 00Z NAM/GFS are close to the consensus taking short wave energy out of Alberta/Manitoba before 09/00Z and tracking it across the Northern Plains Sat. The 00Z NAM becomes faster than the consensus (as does the 12Z UKMET/CMC) after that time, as it appears to feel the edge of the vortex moving into Labrador. The 12Z GFS is closer to the 12Z ECMWF/12Z ECMWF ensemble mean with the movement of the short wave. This blend appears to be the best consensus of mid level solutions. However, there is more spread concerning the track of the surface low that developing ahead of the mid level system, especially toward 10/00Z. Based on the increasing spread of the surface low, forecast confidence is slightly below average. ...Short wave energy crossing Southern CA by the Sun morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average The 00Z NAM/GFS are close to the consensus taking short wave energy from 30N 126W and tracking it toward the Southern CA coast by the end of the period. Given the relatively tight clustering with respect to the mid level feature, a general model blend is preferred, with slightly above average forecast 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