MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 129 AM EST FRI DEC 23 2016 VALID DEC 23/0000 UTC THRU DEC 26/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION WITH FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ISSUES DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. SHORTWAVE MOVING INTO THE PLAINS TODAY AND REACHING THE NORTHEAST ON SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE ONLY MINOR DIFFERENCES EXIST WITH THIS SYSTEM REGARDING ORIENTATION AND SPEED OF AN ELONGATED UPPER TROUGH MOVING TOWARD THE NORTHEAST. A GENERAL MODEL COMPROMISE CAN BE USED TO SMOOTH OUT THE DETAIL DIFFERENCES. TROUGH DIGGING INTO THE WEST ON SAT CYCLONE MOVING INTO SD LATE SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/ECMWF/UKMET BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE ENSEMBLE SPREAD HAS SHRUNK COMPARED TO YESTERDAY REGARDING THE UPPER TROUGH OVER THE WEST VALID 12Z/25-12Z/26. WHILE THE ECMWF AND ITS ENSEMBLE MEAN HAVE REMAINED RELATIVELY CONSISTENT OVER ITS PAST FEW CYCLES...THE GFS HAS BEEN GRADUALLY TRENDING SLOWER THROUGH ITS 00Z RUN TONIGHT. THE 00Z NAM KICKS OUT THE UPPER TROUGH A LITTLE QUICKER THAN THE REMAINING MODEL GUIDANCE AND WHILE MAY BE USABLE AT TIMES...THE 00Z GFS/ECMWF/UKMET ARE CLOSER TO THE MIDDLE GROUND CONSENSUS REPRESENTED BY THE 00Z GEFS AND 12Z ECMWF MEAN. WHILE NOT EXACTLY THE SAME...A BLEND OF THESE 3 MODELS REPRESENTS THE BEST COMPROMISE AT THIS TIME. ONLY MINOR ADJUSTMENTS WERE SEEN BETWEEN THE 12Z AND 00Z ECMWF/UKMET...WITH THE 00Z CMC SOUTH OF THE WPC PREFERENCE. CLOSED MID-LEVEL LOW DROPPING SOUTH OFF OF THE WEST COAST ON SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM/GFS/ECMWF BLEND CONFIDENCE: SLIGHTLY BELOW AVERAGE ENSEMBLE SPREAD WITH THIS SYSTEM IS LARGE...ENCOMPASSING ALL OF THE LATEST DETERMINISTIC GUIDANCE. THE SREF/GEFS/EC MEANS SUPPORT A POSITION NEARER TO THE CA COAST THAN SHOWN BY THE 12Z ECMWF/UKMET/CMC AND CLOSER TO THAT OF THE 00Z NAM/GFS. THE 00Z ECMWF ADJUSTED TOWARD THE NAM WITH THE 00Z GFS A BIT FARTHER AWAY FROM THE COAST AND NORTH SUN NIGHT. A BLEND OF THE NAM/GFS/ECMWF IS CLOSEST TO THE LATEST ENSEMBLE MEAN GUIDANCE. THE LARGE ENSEMBLE SPREAD AND CHANGE OF FLOW ACROSS THE ERN PACIFIC FROM MERIDIONAL TO QUASI-ZONAL REDUCES CONFIDENCE A BIT THROUGH MON MORNING. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO