MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1150 AM 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 AND GFS ...MIDWEST/GREAT LAKES/NORTHEAST... PREFERENCE: BLEND OF THE 00Z ECMWF AND 00Z GEM 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 00Z ECMWF AND 00Z GEM TAKE THE LOW A BIT LEFT OF THE MULTI-MODEL CONSENSUS. THE 12Z GFS IS PERHAPS A TAD EAST OF THE MULTI-MODEL CONSENSUS. OVERALL...THE STRONGER MODEL CLUSTERING FAVORS THE 00Z ECMWF AND 00Z GEM AS THE 00Z ECENS MEAN AND 06Z GEFS MEAN SUGGEST A SOMEWHAT DEEPER SOLUTION AND A TRACK A LITTLE LEFT OF THE GLOBAL MODEL CONSENSUS. ...CALIFORNIA/SOUTHWEST U.S... PREFERENCE: BLEND OF THE 00Z ECMWF AND 00Z 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 SOLUTION AND LIKE THE 12Z GEM IS SEEN AS BEING A LITTLE SLOWER THAN THE MULTI-MODEL CONSENSUS. THE 12Z GFS IS FASTER AND WEAKER THAN THE CONSENSUS...WITH THE 00Z ECMWF AND 00Z UKMET SPLITTING THE DIFFERENCE. THE ECMWF AND UKMET GENERALLY CLUSTER TOGETHER QUITE WELL AND ARE SUPPORTED BY THE 06Z GEFS MEAN AND 00Z ECENS MEAN. ...SOUTHERN/CENTRAL PLAINS WED AND THURS... PREFERENCE: 00Z 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 00Z GEM THE STRONGEST. THE 12Z GFS/00Z UKMET AND 00Z ECMWF SPLIT THE DIFFERENCE...BUT THE UKMET TENDS TO BE ON THE WEAKER END OF THIS SPECTRUM. WPC WILL FAVOR THE IDEA OF AT LEAST AN IDENTIFIABLE SHORTWAVE EJECTING ACROSS THE CENTRAL AND SOUTHERN PLAINS BY THURS. WILL FAVOR THE 00Z ECMWF FOR THE TIME BEING. ...PACIFIC NORTHWEST/NORTHERN ROCKIES... PREFERENCE: BLEND OF THE 00Z ECMWF AND 00Z UKMET 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 00Z GEM AND 12Z GFS SHOW A BIT MORE DEPTH TO THE ENERGY TRAVERSING THE NORTHERN ROCKIES. THE 00Z GEM IS ALSO A BIT SLOWER. THE 00Z ECMWF AND 00Z UKMET ARE A BIT WEAKER...WITH THE 12Z NAM SPLITTING THE DIFFERENCE. THE LATEST GEFS MEAN AND ECENS MEAN TEND TO SUPPORT THE RELATIVELY FLATTER ECMWF/UKMET CAMP...AND SO A BLEND OF THE ECMWF AND UKMET WILL BE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON