MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 242 PM EDT WED JUL 02 2014 VALID JUL 02/1200 UTC THRU JUL 06/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND ECMWF ...TROPICAL STORM ARTHUR... PREFERENCE: 02/15Z NHC FORECAST ADVISORY THE 02/15Z NHC TRACK/TIMING FOR T.S. ARTHUR APPEARS TO GENERALLY BY CLOSEST TO A BLEND OF THE 12Z GEFS MEAN AND THE 12Z GEM THROUGH 48 HRS...AND THEN GENERALLY IN LINE WITH THE 12Z GEM AND 12Z ECMWF BY 72 HRS. THE 12Z NAM IS NOTABLY SLOWER THAN THE OFCL NHC FORECAST FROM 48 HRS ONWARD...AND BY 72 HRS...THE 12Z UKMET IS SLOWER THAN THE OFCL NHC FORECAST. THE 12Z GFS DOES THE OPPOSITE IN BECOMING FASTER THAN ANY MODEL AND THE OFCL NHC FORECAST BY 72 HRS. ...UPPER TROUGH/COLD FRONT SWEEPING THROUGH THE EASTERN U.S.... PREFERENCE: BLEND OF THE 12Z ECMWF/12Z UKMET AND 12Z GEM CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z NAM IS A SLOWER OUTLIER WITH THE PROGRESSION OF THE TROUGH AXIS AS COMPARED TO THE GLOBAL MODEL CONSENSUS. THE 12Z GFS ON THE OTHER HAND IS THE FASTEST SOLN BEYOND 60 HRS...ALTHOUGH IT HAS TRENDED SLOWER. THE 12Z ECMWF/12Z UKMET AND 12Z ECMWF NOW ALL SPLIT THE DIFF BETWEEN THE FASTER GFS AND SLOWER NAM. THE LATEST ECENS MEAN SUPPORTS A SOLN CLOSE TO A BLEND OF THE 12Z ECMWF/12Z UKMET AND 12Z GEM...AND THE LATEST GEFS MEAN STILL SUGGESTS THE LATEST GFS IS TOO PROGRESSIVE. BASED ON THE OVERALL TRENDS AND SPREAD...WILL EXCLUDE THE SLOWER AND FASTER OUTLIERS AS PER THE NAM/GFS SOLNS AND LEAN TWD A NON-NCEP CONSENSUS. ...TROUGHING ALONG THE WEST COAST... PREFERENCE: BLEND OF THE 12Z ECMWF/12Z UKMET CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE LATEST GUIDANCE SHOWS GOOD AGREEMENT ON THE LARGER SCALE WITH THE FORMATION OF A CLOSED LOW ALONG THE WRN BRITISH COLUMBIA COAST THROUGH FRI MORNING BUT DIFFER SOMEWHAT WITH THE SMALLER SCALE SHORTWAVE DETAILS ADVANCING THROUGH THE BASE OF THE OVERALL TROUGH AXIS THAT IMPACTS THE PAC NORTHWEST AND WITH ADDITIONAL SHORTWAVE ENERGY RACING TOWARD THE PAC NORTHWEST THIS WEEKEND. THE BETTER CONTINUITY AGAIN SUPPORTS A SOLN TWD THE 12Z ECMWF AND 12Z UKMET...WITH THE 12Z NAM AND THE 12Z GEM SHOW SOMEWHAT MORE AMPLIFIED WITH SMALLER SCALE SHORTWAVE ENERGY THAT EJECTS ENEWD OUT OF THE BASE OF THE LARGER SCALE TROUGH OFFSHORE THE WEST COAST. THE 12Z GFS HAS TRENDED TWD THE MORE CONSISTENT ECMWF/UKMET CLUSTER...AND IT SHOULD BE NOTED THAT THE GFS/ECMWF AND UKMET CLUSTER BETTER OVER THE GULF OF AK WITH THE MASS FIELD DETAILS OF A REDEVELOPING CLOSED LOW BY SAT. BASED ON BETTER CONTINUITY AND SUPPORT FROM THE GFS...WILL CONTINUING LEANING TWD THE ECMWF/UKMET SOLNS. ...SHORTWAVE DIGGING SOUTHEAST ACROSS THE MIDWEST ON SATURDAY... PREFERENCE: BLEND OF THE 12Z ECMWF/12Z GFS AND 12Z GEM CONFIDENCE: AVERAGE THE MODELS INDICATE A SHORTWAVE TROUGH DIGGING SEWD DOWN THE EAST SIDE OF A FLAT MEAN RIDGE OVER THE FOUR CORNERS AND HIGH PLAINS ON SAT...WITH THE MODELS SUPPORTING IT ADVANCING THROUGH THE MIDWEST. THE 12Z NAM IS A RELATIVELY STRONGER/SLOWER OUTLIER...WITH THE 12Z ECMWF/12Z GFS AND 12Z GEM A TAD WEAKER AND A LITTLE FASTER. THE 12Z UKMET IS THE WEAKEST AND FLATTEST SOLN. BASED ON THE LATEST MODEL CLUSTERING TWD A SOMEWHAT MORE DEFINED SHORTWAVE IMPULSE DIGGING SEWD TWD THE MIDWEST WILL PREFER THE STRONGER CLUSTERING AS SEEN WITH THE ECMWF/GFS AND GEM SOLNS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON