MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1150 PM EST FRI NOV 18 2016 VALID NOV 19/0000 UTC THRU NOV 22/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. NEGATIVELY TILED UPPER TROUGH MOVING THROUGH THE OHIO VALLEY THIS MORNING...CLOSING OFF OVER THE NORTHEAST SUN/MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE LATEST DETERMINISTIC/ENSEMBLE GUIDANCE SHOW SIMILARLY WITH THIS FEATURE. CLOSED LOW OFF OF THE PACIFIC NORTHWEST TODAY...WEAKENING INTO THE PACIFIC NORTHWEST THROUGH SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS SHOW MINOR DIFFERENCES WITH THE TIMING OF THE CORE OF THE REMNANT CLOSED LOW MOVING ACROSS VANCOUVER ISLAND ON SUN. THE 00Z NAM/GFS ARE HELD BACK SLIGHTLY COMPARED TO THE 12Z ECMWF/UKMET/CMC. THE LATEST SREF/GEFS/EC MEANS SUPPORT A TIMING BETWEEN THE SLOWER/FASTER MODEL RUNS...BUT THE DIFFERENCES ARE MINOR ENOUGH TO SUPPORT A GENERAL MODEL COMPROMISE. WEAK SURFACE LOW MOVING WWD ACROSS NOVA SCOTIA INTO NEW BRUNSWICK TONIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THIS FEATURE. MID-UPPER TROUGH AXIS CROSSING CA SUN NIGHT...REACHING THE SRN ROCKIES MON NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z ECMWF/UKMET BLEND CONFIDENCE: AVERAGE THE 00Z GFS IS TOWARD THE FASTER SIDE OF THE GUIDANCE WITH THE UPPER TROUGH ACROSS THE SOUTHWEST U.S. WHICH CAN BE A TYPICAL BIAS SEEN IN THE GFS THIS TIME OF YEAR WITH LARGER SCALE TROUGH SPEEDS. THE 00Z NAM ENDS UP MUCH SLOWER BY TUE MORNING...AND THE 12Z CMC IS ALSO A BIT SLOWER...WHILE ALSO SHOWING A SHARPER TROUGH AXIS BY 12Z/22. THE LATEST ENSEMBLE SPAGHETTI HEIGHTS AND TRENDS SUPPORT A POSITION TOWARD THE MIDDLE...OR NEAR THE 12Z ECMWF/UKMET. REGARDING A SURFACE LOW FORECAST TO DEVELOP IN THE CNTRL PLAINS IN RESPONSE TO THE PROGRESSING UPPER TROUGH...THE LATEST ENSEMBLE CLUSTERING PLACES THIS LOW BETWEEN SWRN KS AND CNTRL KS BY 12Z/22. THE 12Z ECMWF/UKMET ARE WEST OF CENTER WITHIN THE BEST LOW CENTER CLUSTERING HERE...WITH THE 00Z GFS RIGHT OF CENTER. CLOSED LOW APPROACHING BRITISH COLUMBIA TUE MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE THE MODELS SHOW ONLY MINOR TIMING DIFFERENCES WITH THIS SYSTEM...WITH THE 12Z ECMWF TOWARD THE FASTER SIDE OF THE DETERMINISTIC SPREAD. THE 12Z ECMWF MEAN IS AHEAD OF 12Z ECMWF...AND THERE IS CERTAINLY ROOM FOR FUTURE RUNS OF THE SOMEWHAT SLOWER NAM/GFS TO SPEED UP. HOWEVER...GIVEN THE DIFFERENCES ARE RELATIVELY MINOR AT THIS POINT...A GENERAL MODEL COMPROMISE WILL SUFFICE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO