MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1156 PM EST THU DEC 03 2015 VALID DEC 04/0000 UTC THRU DEC 07/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SOUTHERN STREAM ENERGY MOVING INTO THE SOUTHEAST BY SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THERE IS RATHER MINIMAL MASS FIELD SPREAD WITH THIS SYSTEM...AND SO A GENERAL MODEL COMPROMISE IS PREFERRED. PROGRESSIVE SHORTWAVE MOVING THROUGH THE GREAT LAKES AND NORTHEAST TODAY/TONIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THERE IS OVERALL GOOD AGREEMENT AMONG THE MODELS WITH THIS SYSTEM AND THUS A GENERAL MODEL COMPROMISE IS PREFERRED. SPLIT FLOW TROUGH CROSSING THE WEST AND EJECTING OUT INTO THE PLAINS/MIDWEST BY SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM / 12Z ECMWF BLEND CONFIDENCE: AVERAGE ALL OF THE MODELS HAVE BEEN TRENDING NORTH WITH THE SRN STREAM SHORTWAVE EXPECTED TO CROSS THE PLAINS SAT NIGHT BUT THE NAM/GFS HAVE BEEN TRENDING SLOWER...WHILE THE ECMWF/UKMET HAVE BEEN TRENDING FASTER AS THIS TROUGH REACHES THE OHIO VALLEY. BY MON MORNING...12Z/07...THE 00Z GFS REMAINS THE SLOWEST...ALONG WITH THE 18Z GEFS. THE 12Z UKMET REMAINS THE FASTEST BY FAR...WITH THE 00Z NAM...12Z ECMWF AND 12Z CMC SOMEWHERE IN THE MIDDLE. LOOKING AT 12Z/07...ENSEMBLE SPAGHETTI HEIGHT PLOTS INDICATE THE GEFS IS LARGELY ALONE WITH A SLOWER CLUSTERING OF MEMBERS OVER THE MID-MISSISSIPPI VALLEY...FOLLOWED BY A WIDE RANGE OF ECMWF MEMBERS WITH TROUGH AXES RANGING FROM THE LOWER OHIO VALLEY TO JUST OFF OF THE NRN MID-ATLANTIC COAST. THE 12Z ECMWF MEAN APPEARS TO BE A REASONABLE SOLUTION...AND IS A LITTLE SLOWER THAN THE 12Z ECMWF. A BLEND OF THE EVEN SLOWER 00Z NAM AND THE 12Z ECMWF...WHICH IS A POSITION SLIGHTLY SLOWER THAN THE 12Z EC MEAN IS PREFERRED WHICH IS CLOSE TO CONTINUITY. UPPER TROUGH AXIS OFF OF THE WEST COAST SUN MORNING AND OVER THE CNTRL ROCKIES MON MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 12Z CMC BLEND CONFIDENCE: AVERAGE THE 12Z CMC IS FLATTEST WITH THIS SYSTEM. HOWEVER...THE REMAINING DETERMINISTIC MODELS SHOW PRETTY GOOD AGREEMENT WITH SIMILAR TIMING AND ONLY MINOR AMPLITUDE DIFFERENCES. NEXT IN A SERIES OF UPPER TROUGHS APPROACHING THE WEST COAST MON MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM...00Z GFS...12Z ECMWF BLEND CONFIDENCE: BELOW AVERAGE FLOW ACROSS MUCH OF THE PACIFIC IS FORECAST TO BECOME MORE ZONALLY ORIENTED BY EARLY NEXT WEEK...WHICH SHOULD PROMOTE FAST MOVEMENT OF STORMS INTO THE EAST PACIFIC. THERE IS AN INDICATION OF A LOW AMPLITUDE SHORTWAVE TO APPROACH THE WEST COAST...BUT STILL BE OFFSHORE...BY MON MORNING. ENSEMBLE SPAGHETTI SIMILARLY WITH LOW AMPLITUDE BUT DIFFER WITH TIMING. THERE IS NO CLEAR CLUSTERING OF ENSEMBLE MEMBERS WITH THE MOST RECENT CYCLE. INDIVIDUAL DETERMINISTIC MODEL RUN TO RUN CONTINUITY HAS BEEN DECENT...SO THE IDEA IS TO GO TOWARD THE BEST DETERMINISTIC CLUSTERING. GIVEN THE DEEPER 12Z UKMET AND SPLIT-ENERGY 12Z CMC...THE PREFERENCE IS TO GO TOWARD THE SIMILAR NAM/GFS/ECMWF. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO