MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 147 AM EST FRI DEC 05 2014 VALID DEC 05/0000 UTC THRU DEC 08/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND THE ECMWF ...UPPER TROUGH/CYCLONE MOVING INTO THE NORTHWEST FRI NIGHT... PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE DETERMINISTIC AND ENSEMBLE MODEL GUIDANCE HAS CONTINUED TO TREND SLIGHTLY SLOWER/DEEPER WITH THE SHORTWAVE TROUGH REACHING THE PACIFIC NORTHWEST FRI NIGHT...ALTHOUGH THE 00Z NAM CURRENTLY APPEARS TO BE TOO DEEP WITH THE ENERGY AS IT TRAVERSES THE MEAN RIDGE POSITION OVER THE NORTHWEST ON SAT. MODEL SPREAD INCREASES DOWNSTREAM AS THE ENERGY MOVES ACROSS THE NORTHERN ROCKIES AND OUT INTO THE NORTHERN PLAINS. ALL OF THE MODELS SHOW A LOW CENTER DEVELOPING IN THE LEE OF THE FAR NORTHERN ROCKIES...BUT THE 00Z NAM TRACKS ITS LOW WELL TO THE NORTH ACROSS SOUTHERN CANADA. GRADUALLY THE 00Z GEM TAKES ITS SURFACE LOW FARTHER NORTH AS WELL AND EVEN NORTH OF THE NAM SOLN BY EARLY MON OVER CANADA. THE 00 GFS/00Z UKMET AND 00Z ECMWF ARE ALL FARTHER SOUTH...WITH THE 00Z ECMWF AND 00Z GFS THE FARTHEST SOUTH SOLNS WHICH HAVE A TRACK ALONG AND JUST NORTH OF THE U.S. BORDER. REGARDING TIMING...THE UKMET WHICH HAD BEEN A FASTER OUTLIER SOLN WITH ITS LOW DID TREND A LITTLE SLOWER WITH ITS 00Z RUN AND IS CLOSE TO THE 00Z GEM SOLN...WHICH IS JUST A TAD FASTER THAN THE MULTI-MODEL CONSENSUS. THE 00Z GFS AND 00Z ECMWF CLUSTER REASONABLY WELL WITH TIMING. FOR NOW...WITH SOMEWHAT LIMITED CONFIDENCE GIVEN THE LATITUDINAL DIFFS WITH THE LOW TRACK...WILL FAVOR A BLEND OF THE 00Z GFS AND 00Z ECMWF. THE 00Z GFS AND 00Z ECMWF CLUSTER BEST AND ALSO THE ENSEMBLE MEANS INCLUDING THE SREF MEAN...GEFS MEAN AND ECENS MEAN FAVOR A LOW TRACK FARTHER SOUTH IN LINE WITH A DETERMINISTIC GFS/ECMWF BLEND. ...SHORTWAVE MOVING INTO THE SOUTHWEST FRI NIGHT... PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE 00Z UKMET SPED UP ITS SOLN AND IS CLOSE TO THE MULTI-MODEL CONSENSUS WITH THIS SYSTEM AS IT TRAVERSES THE SOUTHWEST ON SAT...AND CROSSES OUT INTO THE SOUTHERN PLAINS THROUGH SUN. SOME MINOR DIFFS RELATIVE TO DEPTH ARE NOTED...BUT WOULD PREFER TO GO WITH A GENERAL MODEL COMPROMISE TO RESOLVE THESE SMALLER SCALE ISSUES ATTM. ...SHORTWAVE TROUGH APPROACHING THE WEST COAST LATE SUN... PREFERENCE: NON-GEM CONSENSUS CONFIDENCE: ABOVE AVERAGE THE MODELS INDICATE ANOTHER PROGRESSIVE PACIFIC SHORTWAVE AND ATTENDANT FRONTAL ZONE ARRIVING ALONG THE WEST COAST BY LATER SUN. THE 00Z GEM IS A TAD STRONGER ALOFT WITH THE ENERGY AND ALSO A LITTLE MORE PROGRESSIVE WITH ITS FRONT AS COMPARED TO THE MULTI-MODEL CONSENSUS. THE REMAINING MODELS ARE REASONABLY WELL CLUSTERED WITH DEPTH AND TIMING...AND ALL OF THE MODELS INDICATE AN INFLUX OF ONSHORE FLOW IMPACTING THE IMMEDIATE COASTAL RANGES OF THE WEST COAST FROM NORTHERN CA NORTH INTO WA BY LATER SUN AND MON. A NON-GEM CONSENSUS WILL BE PREFERRED ATTM. ...SHORTWAVE EJECTING FROM THE CENTRAL/SOUTHERN PLAINS TO THE MID-ATLANTIC... ...SURFACE LOW TRACKING FROM THE SOUTHERN PLAINS TO THE OHIO VALLEY/MID-ATLANTIC... PREFERENCE: BLEND OF THE 00Z GFS AND 00Z ECMWF CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE MODELS ARE IN MUCH BETTER AGREEMENT WITH THIS SHORTWAVE AND CORRESPONDING SURFACE LOW THAT EJECTS OUT OF THE SOUTHERN PLAINS EARLY FRI AND PROGRESSIVELY MOVES DOWNSTREAM THROUGH THE OH VALLEY AND THE MID-ATLANTIC REGION LATER SAT AND EARLY SUN. THE 00Z ECMWF IS A TAD STRONGER THAN THE GLOBAL MODEL CONSENSUS...WITH THE 00Z NAM AND 00Z GEM A BIT WEAKER. THE 00Z GFS AND 00Z UKMET SPLIT THE DIFF. BASED ON SOMEWHAT BETTER MODEL CLUSTERING AND ENSEMBLE SUPPORT WILL CONTINUE TO PREFER A GFS/ECMWF BLEND. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON