MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 152 PM EST MON DEC 15 2014 VALID DEC 15/1200 UTC THRU DEC 19/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND THE ECMWF ...MIDWEST/GREAT LAKES/NORTHEAST... PREFERENCE: BLEND OF THE 12Z ECMWF AND 12Z UKMET CONFIDENCE: AVERAGE THE MODELS REMAIN LOCKED INTO A SOLUTION FOR THE CYCLONE TRACKING TOWARD THE GREAT LAKES. THE UPPER WAVE OPENS DURING INTERACTION WITH A CLOSED LOW FORMING IN THE NORTHERN STREAM FLOW...BUT IS EXPECTED TO FOSTER SECONDARY SURFACE LOW DEVELOPMENT OVER SOUTHERN NEW ENGLAND. THEREAFTER THE MODELS ARE IN VERY GOOD AGREEMENT IN TAKING THE LOW NORTHEAST ACROSS NOVA SCOTIA AND INTO SOUTHEAST CANADA. THE 12Z ECMWF AND 12Z UKMET TAKE THE LOW A BIT LEFT OF THE MULTI-MODEL CONSENSUS TOWARD THE END OF THE PERIOD. THE 12Z GFS IS PERHAPS A TAD EAST OF THE MULTI-MODEL CONSENSUS. THE 12Z NAM AND 12Z GEM SPLIT THE DIFFERENCE. THE 00Z ECENS MEAN FAVORS THE ECMWF/UKMET CAMP...WITH THE 12Z GEFS MEAN FAVORING THE DETERMINISTIC GFS. WILL LEAN TOWARD THE NON-NCEP CAMP WITH A PREFERENCE TOWARD THE ECMWF AND UKMET. ...CALIFORNIA/SOUTHWEST U.S... PREFERENCE: BLEND OF THE 12Z ECMWF AND 12Z UKMET CONFIDENCE: AVERAGE AT THE LEADING EDGE OF AN AMPLIFYING PACIFIC JET...THE MODELS CONTINUE TO SHOW A FAIR DEGREE OF SPREAD WITH RESPECT TO TIMING AND DEPTH OF THE SHORTWAVE ENERGY TRAVERSING THE SOUTHWESTERN U.S. INVOLVING THE SOUTHERN STREAM FLOW. THE MODELS SUGGEST A LARGER SCALE SOUTHERN STREAM TROUGH WILL EVOLVE BY DAY 2/WED AND DAY 3/THURS OVER THE SOUTHWEST AND ADJACENT FOUR CORNERS REGION. THE 12Z NAM IS A STRONGER OUTLIER ...AND THE 12Z GEM IS A SLOW OUTLIER. THE 12Z GFS IS FASTER AND WEAKER THAN THE MULTI-MODEL CONSENSUS...WITH THE 12Z ECMWF AND 12Z UKMET SPLITTING THE DIFFERENCE. HOWEVER...THE ECMWF AND UKMET HAVE BOTH TRENDED A LITTLE SLOWER OWING TO A SLIGHTLY STRONGER SHORTWAVE TROUGH DIGGING INTO THE FOUR CORNERS. BASED ON THE ECMWF AND UKMET GENERALLY CLUSTERING TOGETHER QUITE WELL...AND WITH SUPPORT FROM THE 12Z GEFS MEAN AND 00Z ECENS MEAN...A BLEND OF THESE TWO SOLUTIONS WILL BE PREFERRED. ...SOUTHERN/CENTRAL PLAINS WED AND THURS... PREFERENCE: 12Z ECMWF CONFIDENCE: AVERAGE AHEAD OF THE SOUTHWEST U.S. TROUGH A LEAD SHORTWAVE IS LIKELY TO REACH THE PLAINS BY WED. THIS IS THE SYSTEM CURRENTLY MOVING INTO CALIFORNIA. THE MODELS SUGGEST A GRADUAL DEAMPLIFICATION OF THE SHORTWAVE AS IT ENCOUNTERS INCREASINGLY CONFLUENT FLOW DOWNSTREAM. THE 12Z NAM BECOMES THE WEAKEST SOLUTION AS THE ENERGY TRAVERSES PLAINS...WITH THE 12Z GEM THE STRONGEST. THE 12Z GFS/12Z UKMET AND 12Z ECMWF SPLIT THE DIFFERENCE. WPC WILL FAVOR THE IDEA OF AT LEAST AN IDENTIFIABLE SHORTWAVE EJECTING ACROSS THE CENTRAL AND SOUTHERN PLAINS BY THURS. WILL FAVOR THE 12Z ECMWF OWING TO GENERALLY BETTER CONTINUITY. ...PACIFIC NORTHWEST/NORTHERN ROCKIES... PREFERENCE: BLEND OF THE 12Z NAM/12Z UKMET AND 12Z ECMWF CONFIDENCE: AVERAGE THE FORECAST RATIONALE HERE IS MUCH THE SAME AS THAT STATED IN THE CALIFORNIA/SOUTHWEST U.S. SECTION ABOVE. THOUGH THE INDIVIDUAL SHORTWAVES ARE LESS WELL DEFINED IN THE NORTHERN STREAM...THERE ARE INDICATIONS THAT ONE TROUGH SHOULD BE LIFTING THROUGH THE NORTHERN ROCKIES AND ANOTHER SHOULD BE MOVING INTO THE PACIFIC NORTHWEST ON DAYS 2/3. THE 12Z GEM AND 12Z GFS SHOW A BIT MORE DEPTH TO THE ENERGY TRAVERSING THE NORTHERN ROCKIES. THE 12Z GEM IS ALSO A BIT SLOWER. THE 12Z NAM/12Z ECMWF AND 12Z UKMET ARE ALL CLUSTERED TOGETHER WITH A MODESTLY WEAKER SOLUTION. THE LATEST GEFS MEAN AND ECENS MEAN TEND TO SUPPORT THE RELATIVELY FLATTER ECMWF/UKMET/NAM CAMP...AND SO A BLEND OF THESE SOLUTIONS WILL BE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON