Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 1122 PM EST Tue Jan 22 2019 Valid Jan 23/0000 UTC thru Jan 26/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation with Preliminary Preferences ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Pattern across the CONUS... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z GFS...possibly blended with NAM, ECMWF at times A storm system will lift through the Great Lakes into Canada. Another wave along the trailing front will affect the Mid-Atlantic states and New England Wed/Thu. This is followed by a period of deep and broad cyclonic flow / troughing blanketing much of the nation, with high pressure generally dominant in the low levels. During the early part of the short range period models are seemingly in strong agreement, the main exception being the NAM which is a few millibars deeper at the surface as the secondary frontal wave moves up through New England toward 25/00Z. This depth issue does have some impact on the precipitation forecast. Larger scale differences show up mainly out west on Days 2 and 3. A shortwave tops the west coast mean ridge position and then dives south. There is some systematic difference in how the GFS, ECMWF handle this. Viewing spaghetti plots over the past three cycles the ECMWF and its ensemble are unwavering in being faster and less sharp with the wave, taking it to near southwest Texas by 26/12Z, and inducing warmer heights and flattening of the cyclonic flow downstream in the eastern states. The GFS/GEFS and also the NAM are equally unwavering in being slower and sharper, digging the wave into Arizona at 26/12Z, and leaving the cyclonic flow intact downstream a while longer. There is perhaps no strong synoptic or science reason to favor one over the other, but experience this week has been that the ECMWF is moving waves too quickly through the ridge position. Looking at advections through each time step the NCEP guidance looks good, and we are inclined to lean more toward that guidance - particularly the GFS, whereas the NAM displays the depth issue over New England and is then also a bit deep and cold with its thermal fields over the southern Plains on Days 2, 3. One could, however, blend the GFS with the ECMWF to arrive at a more objective consensus. Certainly the 12Z UKMET and Canadian were even faster and less sharp than the ECMWF in the Southwest, so we steered away from those models in our preference. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Burke