MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 249 AM EDT TUE OCT 18 2016 VALID OCT 18/0000 UTC THRU OCT 21/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ COLD FRONT CROSSING THE GREAT LAKES/NEW ENGLAND TODAY/TONIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL BLEND CONFIDENCE: ABOVE AVERAGE THE MODELS SHOW SIMILARLY WITH THIS SYSTEM. UPPER TROUGH REACHING THE CNTRL ROCKIES WED MORNING EVENTUAL SURFACE LOW NEAR THE OHIO VALLEY THU MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/00Z ECMWF BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE THE 00Z UKMET/CMC BOTH TRENDED SLOWER FROM THEIR PREVIOUSLY QUICKER SOLUTIONS REGARDING THE TIMING OF THE UPPER TROUGH EAST OF THE ROCKIES ON THU. JUST THE 00Z UKMET STANDS OUT AS SIGNIFICANTLY FASTER THROUGH THU WITH THE 00Z CMC NOW ON THE SLOWER AND DEEPER SIDE OF THE DETERMINISTIC SPREAD. THE 12Z ECMWF/GEFS/EC ENSEMBLE SPAGHETTI HEIGHTS SHOW THE GEFS SLOWER/MORE AMPLIFIED WITH THE UPPER TROUGH BY FRI MORNING COMPARED TO THE FLATTER/MORE PROGRESSIVE ECMWF MEMBERS. THE CMC ENSEMBLES SHOW SOME MEMBERS SLOWER/DEEPER THAN THE GEFS AND AS FAST/FLAT AS THE ECMWF. WITH A DEAMPLIFYING EASTERN PACIFIC JET STREAM...THERE IS CERTAINLY ROOM FOR A QUICKER PROGRESSION OF THE TROUGH THAN SHOWN BY THE 00Z GFS/NAM...BUT TRENDS ON THE 00Z DETERMINISTIC GUIDANCE SEEM TO BE SHOWING CONVERGENCE TOWARD A MIDDLE GROUND. SOMEWHERE TOWARD THE MIDDLE OF THE SPREAD SEEMS BEST...OR A BIT SLOWER THAN THE 12Z EC MEAN. SO WHILE CONFIDENCE IS LOW...ADJUSTMENTS BY THE 00Z ECMWF/UKMET/CMC HAVE RAISED CONFIDENCE SLIGHTLY IN A 00Z GFS/ECMWF BLEND. DEEP UPPER LEVEL LOW IN THE GULF OF AK THROUGH THU MORNING WITH ONSHORE FLOW INTO THE PACIFIC NORTHWEST AHEAD OF E-PAC COLD FRONT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE DIFFERENCES ARE NOT TOO GREAT ACROSS THE ERN PACIFIC...BUT THE 00Z ECMWF IS ON THE QUICKER SIDE OF THE DETERMINISTIC ENVELOPE REGARDING COLD FRONTAL TIMING INTO THE PACIFIC NORTHWEST THU MORNING. GIVEN THE MODEL DIFFERENCES ARE MINOR...A GENERAL MODEL COMPROMISE SHOULD WORK WELL FOR THIS SYSTEM LATE WED INTO FRI. MID-LEVEL LOW CLOSING OFF NEAR THE BAHAMAS TUESDAY RELATED SURFACE LOW IN THE WRN ATLANTIC ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/ECMWF BLEND CONFIDENCE: AVERAGE THE 00Z CMC IS JOINED BY A MINORITY OF ENSEMBLE MEMBERS REGARDING ITS STRONGER AND WWD DEPICTION OF THE MID-LEVEL LOW OFF OFF THE SERN COAST THU EVENING. THE DEVELOPMENT OF THIS SYSTEM IS IMPACTED BY THE UPSTREAM TROUGH OVER THE ERN U.S. SO SIMILAR TO SECOND SECTION OF THIS DISCUSSION...TRENDS HAVE BEEN FASTER WITH THE ERN U.S. TROUGH...AND THEREFORE TRENDS IN THE SURFACE LOW HAVE GENERALLY BEEN EAST THROUGH FRI MORNING. GIVEN THE UPSTREAM PREFERENCE...AND RULING OUT UNLIKELY SOLUTIONS GIVEN ENSEMBLE DISTRIBUTION...A 00Z GFS/00Z ECMWF BLEND IS CONSIDERED MOST LIKELY WITH THIS SYSTEM IN THE WRN ATLANTIC. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO