Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1146 PM EST Sat Jan 25 2020 Valid Jan 26/0000 UTC thru Jan 29/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preliminary Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Deep closed low moving across the Northeast through Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-NAM blend Confidence: Above average Outside of the 00Z NAM which lags west of the consensus, the global models are in very good agreement with the strong upper low moving into Canada Monday and then opening before ejecting towards Newfoundland Tuesday. ...Shortwave digging from the Northern Plains today to off the Mid-Atlantic coast Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 12Z ECMWF/ECENS/UKMET blend Confidence: Average A sharp shortwave dropping through the Northern Plains will dive quickly southeast and round the base of the longwave trough centered over New England. This feature will move quickly through the Ohio Valley and be off the Mid-Atlantic coast by Tuesday. The CMC is a fast/sheared outlier compared to the remaining guidance and should not be included. Of the remaining models, there exists an NCEP vs Non-NCEP camp as the NCEP models are a bit stronger and faster than the Non-NCEP solutions. The ECENS and GEFS are more in line with the slower solutions, so favor the Non-NCEP camp for this feature as it shifts east through early in the week. ...Trough lifting into the West today and deepening across the Southern Plains by Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Non-CMC/UKMET blend Confidence: Slightly below average The models all take a progressive split-flow trough across the West Coast on Sunday, with a southern stream portion of the energy then dropping down across the Southwest and amplifying into a closed low as it approaches the southern High Plains by early Tuesday. The 12Z CMC is an outlier as it is likely too strong/slow and too far north with the southern stream energy. The 12Z UKMET also appears to be too slow/deep and like the CMC tends to support a bit more interaction between northern and southern stream troughs late in the period. The NAM/GFS and ECMWF all favor a bit more stream separation at least through this period with just some subtle northern/southern stream trough interaction at the very end of the period as the energy approaches the MS Valley. Will prefer a blend of the NAM/GFS and ECMWF at this time given they still tend to have the stronger ensemble support. ...Trough moving onshore the West Tuesday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: Blend of ECENS/GEFS means Confidence: Average Yet another in a series of Pacific shortwave troughs will arrive on Tuesday across the Pacific Northwest. There is considerable spread in intensity of this feature despite reasonable agreement in timing on D3. The ensemble means are in generally good agreement and are favored outside of any operational model which show a wide variation in solutions in the fast mid/upper flow. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Weiss