MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1224 PM EST WED DEC 02 2015 VALID DEC 02/1200 UTC THRU DEC 06/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS AND UKMET ...DEEP CLOSED LOW EJECTING FROM THE CENTRAL PLAINS TO THE NORTHEAST... ...LOW PRESSURE NEAR THE CENTRAL APPALACHIANS LIFTING THROUGH NEW ENGLAND... ...DEEPENING LOW OVER THE GULF OF MAINE... PREFERENCE: BLEND OF THE 12Z GFS AND 12Z UKMET CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS ARE IN GOOD AGREEMENT IN DRIVING A RATHER DEEP UPPER TROUGH AND ASSOCIATED CLOSED LOW EAST THROUGH THE GREAT LAKES AND OH VALLEY THROUGH TONIGHT AND THEN ACROSS THE INTERIOR OF THE NORTHEAST ON THURS. THIS WILL FOSTER DEVELOPING LOW PRESSURE NEAR THE CENTRAL APPALACHIANS TODAY WHICH WILL LIFT NORTHEAST INTO NEW ENGLAND TONIGHT AND THURS. BY LATER THURS...THE LOW CENTER IS EXPECTED TO REACH THE GULF OF MAINE AND INTENSIFY WHILE APPROACHING NOVA SCOTIA. THE 12Z NAM IS A LITTLE NORTH OF THE MULTI-MODEL CONSENSUS AS IT CROSSES NEW ENGLAND ON THURS AND THROUGH THE GULF OF MAINE. THE NAM IS ALSO A LITTLE FASTER THAN THE GLOBAL MODELS. THE 12Z GFS HAS TRENDED MORE PROGRESSIVE AND WHILE IT IS NOT QUITE AS FAST AS THE NAM...IT IS A TAD FASTER THAN THE 00Z ECMWF AND 00Z CMC SOLUTIONS. THE 12Z UKMET HAS TRENDED A LITTLE FASTER COMPARED TO ITS PREVIOUS RUN AND IS ONLY A LITTLE SLOWER THAN THE GFS. WILL PREFER A 12Z GFS/12Z UKMET BLEND AT THIS POINT. ...SOUTHERN STREAM ENERGY CROSSING THE SOUTHERN PLAINS AND MOVING INTO THE SOUTHEAST BY SAT... PREFERENCE: NON-CMC CONSENSUS CONFIDENCE: ABOVE AVERAGE SOUTHERN STREAM SHORTWAVE ENERGY SEPARATING OUT FROM THE WESTERLIES WILL DROP EAST-SOUTHEAST ACROSS PORTIONS OF THE SOUTHERN PLAINS/LOWER MS VALLEY AND THEN INTO THE SOUTHEAST FRI AND SAT. THE 00Z CMC BECOMES A DEEPER OUTLIER WITH THIS SYSTEM...AND WITH THE REMAINING GUIDANCE REASONABLY WELL CLUSTERED...A NON-CMC CONSENSUS WILL BE PREFERRED. ...SHALLOW PROGRESSIVE WAVE IMPACTING SOUTHERN CANADA/U.S. NORTHERN TIER THROUGH THURS... ...ENERGY MOVING THROUGH THE GREAT LAKES/NORTHEAST ON FRI... PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF CONFIDENCE: AVERAGE A SHORTWAVE CURRENTLY MOVING THROUGH BRITISH COLUMBIA CROSSES THE CANADIAN ROCKIES AND SKIRTS THE NORTHERN TIER OF THE U.S. THROUGH THURS WITH SOME SHORTWAVE ENERGY. THE ENERGY THEN AMPLIFIES SOMEWHAT ON ITS WAY ACROSS THE GREAT LAKES AND NORTHEAST THROUGH FRI. THE 12Z NAM AND 00Z CMC APPEAR TO BE A BIT TOO WEAK WITH THE ENERGY COMPARED TO THE MULTI-MODEL CONSENSUS. STRONGER MODEL CLUSTERING RESIDES WITH THE 12Z GFS/12Z UKMET AND 00Z ECMWF...BUT THE UKMET APPEARS TO BE TOO AMPLIFIED ON FRI AS THE ENERGY CROSSES NORTHERN NEW ENGLAND. WILL THEREFORE PREFER A BLEND OF THE GFS AND ECMWF. ...SURFACE LOW APPROACHING WESTERN ORE ON THURS... ...SPLIT FLOW TROUGH CROSSING THE WEST ON FRI... ...ENERGY OVER THE PLAINS ON SAT... PREFERENCE: BLEND OF THE 12Z UKMET AND 00Z ECMWF...THROUGH 48 HOURS BLEND OF THE 12Z GFS AND 00Z ECMWF...AFTER 48 HOURS CONFIDENCE: SLIGHTLY BELOW AVERAGE THE MODELS SHOW A PROGRESSIVE SPLIT FLOW TROUGH CROSSING THE WEST THROUGH THURS AND FRI BEFORE THEN EJECTING OUT INTO THE PLAINS ON SAT. DIFFERENCES BEGIN TO SHOW UP RATHER EARLY IN THE PERIOD AND ESPECIALLY BY LATE THURS WITH LOW PRESSURE WRAPPING UP JUST OFF THE WEST COAST AND MOVING INTO WESTERN ORE THURS NIGHT. THE 12Z GFS APPEARS TO BE TOO PROGRESSIVE WITH THIS WAVE IN LIFTING IT NORTH UP OFF THE PACIFIC NORTHWEST COAST. THE 12Z NAM IS A BIT SLOWER...BUT THE NON-NCEP MODELS ARE ALL A BIT STRONGER AND SLOWER WITH THE LOW CENTER. THE NON-NCEP GUIDANCE SUGGESTS A MORE COMPACT BUT VIGOROUS LOW CENTER APPROACHING WESTERN ORE BY LATE THURS. THE LATEST GEFS MEAN DOES NOT REFLECT THE STRONGER REFLECTION OF THE NON-NCEP SOLUTIONS...BUT THE LATEST ECENS MEAN ACTUALLY DOES TEND TO SUPPORT. WILL PREFER THE CLUSTERING OF THE 12Z UKMET AND 00Z ECMWF AT THIS POINT. DOWNSTREAM AS THE ENERGY CROSSES THE INTERMOUNTAIN WEST AND OUT INTO THE PLAINS...THE 12Z GFS AND 00Z ECMWF COUPLED WITH THE GEFS MEAN AND ECENS MEAN SHOW BETTER CLUSTERING AROUND A SPLIT PATTERN WITH A SOMEWHAT SLOWER AND GENERALLY MORE AMPLIFIED SOLUTION. THE 12Z NAM/12Z UKMET AND 00Z CMC ALL HAVE A BIT OF A FASTER TROUGH PROGRESSION. WILL PREFER A BLEND OF THE 12Z GFS AND 00Z ECMWF AFTER 48 HOURS AS THIS ENERGY TRAVERSES THE INTERIOR OF THE WEST AND OUT INTO THE PLAINS. ...DEEP TROUGH/FRONT APPROACHING THE WEST COAST ON SAT... PREFERENCE: BLEND OF THE 12Z GFS AND 00Z ECMWF CONFIDENCE: AVERAGE THE MODELS INDICATE THE NEXT IN A SERIES OF RATHER DEEP TROUGHS APPROACHING THE WEST COAST ON SAT. HOWEVER...THERE IS SOME SPREAD WITH THE DETAILS OF THE CLOSED LOW OVER THE GULF OF AK THAT IS DRIVING THIS. THE 12Z GFS/12Z UKMET AND 00Z ECMWF ARE A BIT STRONGER WITH THE CLOSED LOW FEATURE VERSUS THE 12Z NAM AND 00Z CMC. ALL OF THE MODELS SHOW A FRONT APPROACHING THE NORTHWEST BY SAT...WITH SOME RELATIVELY MINOR TIMING DIFFERENCES. WILL PREFER A BLEND OF THE 12Z GFS AND 00Z ECMWF AT THIS POINT GIVEN BETTER ENSEMBLE SUPPORT AND MODEL CLUSTERING. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON