Model Diagnostic Discussion NWS Weather Prediction Center College Park MD 147 AM EST Sat Mar 09 2019 Valid Mar 09/0000 UTC thru Mar 12/1200 UTC ...See NOUS42 KWNO (ADMNFD) for the status of the upper air ingest... 00Z Model Evaluation Including Final Preferences and Confidence ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ...Positively tilted shortwave trough moving east into Manitoba and Ontario this weekend... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM, 00Z GFS, 00Z ECMWF and 12Z UKMET blend Confidence: Slightly above average ...07Z update... The 00Z UKMET slowed down appreciably with the shortwave while the 00Z CMC made only small adjustments to its 12Z run. With the 00Z ECMWF very similar to its previous run, will maintain the previous thinking with a preferred blend of the 00Z NAM, 00Z GFS, 00Z ECMWF and 12Z UKMET. ...previous text follows... The 12Z CMC stands out from the remaining guidance with a stronger and somewhat slower trough axis moving through Manitoba on Sunday. The CMC has been trending toward the consensus but it doesn't appear to be there just yet. Will favor a non 12Z CMC blend for this system. ...Surface low tracking across the Upper Midwest/Great Lakes through Sunday... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: non 12Z CMC blend Confidence: Slightly above average ...07Z update... The 00Z CMC made minor adjustments toward the preferred remaining model consensus but remains different enough with placement to keep it out of the preference. No significant changes were noted in the 00Z ECMWF/UKMET compared to their previous 12Z cycles. ...previous text follows... Fairly good agreement in the deterministic and ensemble guidance with this system, but the 12Z CMC is displaced west of the consensus with its 500 mb low by Sunday morning over the Great lakes region. This affects the 850-700 mb low placement in the 12Z CMC through Sunday/Sunday night with a westward deviation from the remaining consensus. A non 12Z CMC blend shows good agreement and is recommended here. ...Closed low over Washington this morning, interacting with the next Pacific trough/surface low nearing California later today, developing into a large closed low over or just offshore of California Monday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: General model blend Confidence: Slightly above average ...07Z update... The 00Z CMC adjusted toward the remaining model consensus with only minor differences noted in the latest 00Z suite of guidance. Therefore, a general model blend is preferred for this system. ...previous text follows... The ECMWF ensemble mean has shown excellent continuity with the timing of the eventual large closed low forecast to develop near the California coast through Sunday night. Meanwhile, the past 4 12/00Z cycles of the GEFS has trended slower to match the ECMWF members. Only the 12Z CMC and a couple of ECMWF ensemble members remain fast through Tuesday morning. Decent agreement is in place with a non-12Z CMC blend. ...Progressive upper trough approaching the Pacific Northwest Tuesday morning... ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Preference: 00Z NAM, 00Z GFS, 12Z ECMWF blend Confidence: Average ...07Z update... The 00Z CMC adjusted slower toward the remaining model consensus with the 00Z ECMWF/UKMET adjusting a bit less amplified with the shortwave near the Pacific Northwest Tuesday morning. Given good agreement present with the observed shift from the CMC, a general model blend is now recommended for this system. ...previous text follows... Model agreement is not as good with this system compared with the ones above. The ensemble means differ on the timing of the next shortwave trough to affect the Pacific Northwest Monday night into Tuesday. The 12Z ECMWF mean is faster than the 12/18Z GEFS with the 21Z SREF slowest. The latest deterministic guidance is within the relatively tight packing of ensemble members through 12Z/12 except for the faster 12Z CMC. A blend on the non 12Z CMC models is recommended. Model trends at www.wpc.ncep.noaa.gov/html/model2.shtml 500 mb forecasts at www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml Otto