Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 240 PM EST Sun Nov 10 2019 Valid Nov 10/1200 UTC thru Nov 14/0000 UTC ..See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... ...12Z Model Evaluation with Preferences and Confidence... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Amplifying mid-level trough axis into the north-central U.S. for Monday... ...Surface low in the vicinity of New England Tuesday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z UKMET blend Confidence: Average 19Z update: The 12Z UKMET trended faster with its trough axis moving through New England, ahead of the rest of the guidance. The 12Z ECMWF/CMC are in good agreement with the GFS/NAM at 500 mb. At the surface, overall spread has lessened, and the non-UKMET blend preference remains. ---previous discussion--- In the last 24 hours, model agreement has improved with the shortwave trough axis swinging through the Great Lakes and Northeast U.S. through Tuesday and with the surface low development and track across New England. The consensus is for low pressure to develop across the central Appalachians and then toward southern New England by 12Z Tuesday and then enter the Gulf of Maine toward 00Z Wednesday. Spread between the deterministic models is low and overall a general model blend can be used for the mass fields with this system. ...Cold front nearing the Pacific Northwest on Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: GFS/ECMWF blend Confidence: Slightly above average 19Z Update: The 12Z deterministic EC run improved with timing/strength compared to its earlier run, and now agrees well with the rest of the guidance, so some of the its solution can be incorporated into the blend. --- Ridging currently anchored over the western U.S. at the start of the forecast period will break down as a shortwave trough and associated cold front enter the Pacific Northwest Tuesday. Through 48 hours (12.12Z), there is above average agreement with the latest deterministic guidance. Beyond that, the 00Z ECMWF continues to be a bit deeper/amplified with its trough. The 00Z ECENS mean would be a good compromise to the more amplified ECMWF and also agrees well with the latest GFS. The NAM/CMC offer some utility as well while the UKMET seems to be too slow compared to the rest of the guidance. The preference for now will be a non-UKMET blend, with heavier weights toward the ECENS/GFS. ...Closed low over northwestern Mexico... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z UKMET blend Confidence: Average 19Z update: The UKMET is not as big of an outlier as the earlier run suggested, but by the end of the forecast period, it continues to be a little ahead of the rest of the guidance. So, for now will continue the non-UKMET blend preference. ---previous discussion--- The 00Z UKMET continues to be the faster outlier regarding the 500 mb low track across Mexico during the next few days. The 12Z GFS/NAM offer similar solutions to the 00Z ECMWF/CMC, so with this in mind, a non-00Z UKMET blend is preferred. ...Shortwave trough approaching California mid-week... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Average A shortwave trough will approach the western U.S. coast by mid to late week. All of the deterministic guidance has this feature but with some considerable spread in the timing. The usual biases are noted, with the GFS/NAM way out ahead compared to the non-NCEP guidance. The ECMWF is the slowest, while the UKMET/CMC offer a solution near consensus. Relative strength/position looks similar, so a general model blend would likely yield a good approach at this time. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Taylor