MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1123 AM EST FRI NOV 11 2016 VALID NOV 11/1200 UTC THRU NOV 15/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION AND PRELIMINARY PREFERENCES SHORTWAVE TROUGH MOVING ASHORE THE NORTHWEST TONIGHT... MODELS SHOW GOOD LARGE-SCALE AGREEMENT. LOW PRESSURE NEARING THE NORTHWEST COAST MONDAY... PREFERENCE: 1/2 EACH NAM/00Z ECMWF CONFIDENCE: LOW MODELS SHOW CONSIDERABLE RUN-TO-RUN VARIABILITY WITH SYSTEM DETAILS...THUS CONFIDENCE IS LOW WITH ANY RECOMMENDATION. REGARDING DIFFERENCES...THE NAM IS CLOSEST TO THE 00Z ECMWF WITH A FASTER AND FLATTER SOLUTION AND THUS A WEAKER LOW...WHILE THE GFS IS CONSIDERABLY MORE AMPLIFIED IN THE MID LEVELS AND THEREFORE STRONGER WITH THE LOW AND WARMER AHEAD OF IT. ALTHOUGH SUPPORTED BY THE 00Z UKMET/00Z CANADIAN...LESS THAN 10 PERCENT OF THE GLOBAL ENSEMBLE MEMBERS AGREE. THUS...OVERALL THE GFS APPEARS AS A LOW PROBABILITY SCENARIO AT THIS TIME. AT THE MOMENT...UNTIL STRONGER SUPPORT FOR AN ALTERNATIVE APPROACH DEVELOPS...RECOMMEND A FASTER/FLATTER/WEAKER SOLUTION LIKE THE NAM OR ECMWF. SHORTWAVE TROUGH INFLUENCING THE SOUTHEAST MONDAY... PREFERENCE: 1/3 EACH GFS/00Z ECMWF/00Z UKMET CONFIDENCE: AVERAGE THE NAM AND GFS HAVE TRENDED TOWARD GREATER AMPLIFICATION...SEPARATION...AND EASTWARD MOTION OF THE SPLITTING SHORTWAVE TROUGH AS IT CROSSES THE OH/TN VALLEYS ALTHOUGH DIFFER WITH THEIR DETAILS. BY MONDAY...THE NAM WEAKENS THE REMNANT MID LEVEL CENTER AND SENDS IT QUICKLY ACROSS THE EAST COAST WHILE REFORMING A SECONDARY CENTER FARTHER WEST AND MORE TOWARD THE WESTERN EDGES OF THE GUIDANCE. MEANWHILE...THE GFS MAINTAINS A SLOWER AND MORE CONSOLIDATED CENTER MORE ALIGNED WITH THE ECMWF AND UKMET AND ALSO CLOSER TO THE CONSENSUS. GIVEN SLIGHTLY STRONGER MODEL SUPPORT FOR THE GFS/ECMWF AND THAT THE GFS PERHAPS INITIALIZED SLIGHTLY BETTER OVER THE GREAT LAKES AND UPPER MIDWEST COMPARED TO THE NAM USING MID LEVEL DIAGNOSTICS...THE RECOMMENDATION IS FOR A 3-WAY AVERAGE INVOLVING THE 12Z GFS/00Z ECMWF/00Z UKMET. CONFIDENCE IS ONLY AVERAGE GIVEN CONTINUED BUT REDUCED SPREAD. JOINING THE NAM FOR A LOWER PROBABILITY SOLUTION IS THE 00Z CANADIAN...WHICH IS NEAR THE DEEP EDGES OF THE GUIDANCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... JAMES