MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 248 PM EDT THU JUL 03 2014 VALID JUL 03/1200 UTC THRU JUL 07/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING THE NAM/GFS/UKMET/GEM AND ECMWF ...HURRICANE ARTHUR... PREFERENCE: 03/15Z NHC FORECAST ADVISORY OF THE 12Z GUIDANCE...THE 12Z NAM IS CLOSEST TO THE OFCL NHC TRACK THROUGH ABOUT 24 HRS. THEREAFTER...THE 12Z UKMET THROUGH ABOUT 72 HRS IS THE CLOSEST. THE 12Z NAM GRADUALLY ENDS UP RIGHT OF THE OFCL NHC TRACK AND SLOWER. THE 00Z ECMWF HAD BEEN SLOWER AND FARTHER RIGHT AS COMPARED TO THE GLOBAL MODEL SUITE. THE 12Z GFS FROM A TIMING STAND POINT AGREES WELL WITH THE NHC FCST UNTIL ABOUT 48 HRS AND BEYOND WHEN IT BECOMES FASTER THAN NHC. HOWEVER...THERE ARE SOME NOTABLE TRENDS OUT OF THE 12Z MODEL SUITE. THE 12Z GFS...12Z UKMET AND ESP THE 12Z GEM/12Z ECMWF SOLNS HAVE ALL SHIFTED THEIR TRACKS OF ARTHUR TO THE LEFT OF THEIR PREV SOLNS...AND ARE LEFT OF THE OFCL NHC TRACK. AS MENTIONED...THE 12Z UKMET THOUGH APPEARS OVERALL TO BE CLOSEST TO THE NHC TRACK AFTER 24 HRS AND THROUGH ABOUT 72 HRS. ...UPPER TROUGH/COLD FRONT SWEEPING THROUGH THE EASTERN U.S.... PREFERENCE: BLEND OF THE 12Z GFS/12Z ECMWF CONFIDENCE: ABOVE AVERAGE THERE IS BETTER AGREEMENT ON THE LARGER SCALE WITH THE DETAILS OF THE UPPER TROUGH AND ASSOCD COLD FRONT ADVANCING TWD AND THEN CROSSING THE EAST COAST OVER THE NEXT 48 HOURS. THE STRONGEST HEIGHT FALLS ARE EXPECTED TO CROSS THE MID-ATLANTIC AND NORTHEAST AND EVENTUALLY CAPTURING HURRICANE ARTHUR AS ARTHUR RECURVES AWAY FROM THE EAST COAST AND APPROACHES THE CANADIAN MARITIMES. THE 12Z NAM IS A LITTLE FASTER THAN THE GLOBAL MODEL CONSENSUS IN PIVOTING THE HEIGHT FALLS THROUGH THE NORTHEAST...WITH THE 12Z GFS/12Z UKMET/12Z GEM AND 12Z ECMWF A TAD SLOWER BUT VERY WELL CLUSTERED. THE GEFS MEAN AND ECENS MEAN SUPPORT THEIR RESPECTIVE DETERMINISTIC SOLNS RELATING STRICTLY TO THE MASS FIELD DETAILS OF THE UPPER TROUGH/FRONT...HOWEVER...THERE ARE MORE COMPLEX DIFFS NOTED WITH THE CAPTURING OF HURRICANE ARTHUR GIVEN MODEL SPREAD WITH THE TRACK OF ARTHUR IN ITSELF. PLS CONSULT THE LATEST NHC FORECAST ADVISORY FOR DETAILS ON HURRICANE ARTHUR...BUT RELATING TO THE INITIAL ARRIVAL OF THE UPPER TROUGH...A GFS/ECMWF BLEND WILL BE PREFERRED. ...TROUGHING ALONG THE WEST COAST... PREFERENCE: BLEND OF THE 12Z ECMWF/12Z UKMET CONFIDENCE: 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 STILL 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 12Z ECMWF AND 12Z UKMET STILL REFLECT RATHER GOOD MODEL CONTINUITY RUN TO RUN AS COMPARED TO THAT OF THE 12Z NAM AND TO A LESSER EXTENT THE 12Z GFS. THE 12Z NAM AND 12Z GEM BOTH CONTINUE TO SUGGEST SOMEWHAT STRONGER SHORTWAVE IMPULSES EJECTING ACROSS THE PAC NORTHWEST VERSUS THE FLATTER 12Z ECMWF/12Z UKMET AND 12Z GFS. WILL CONTINUE TO PREFER A BLEND OF THE ECMWF/UKMET SOLNS ATTM BASED ON BETTER CONTINUITY AND AT LEAST SOME SUPPORT FROM THE GFS. ...SHORTWAVE DIGGING SOUTHEAST ACROSS THE MIDWEST/OH VALLEY THROUGH THE WEEKEND... PREFERENCE: NON-UKMET CONSENSUS 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 THIS WEEKEND...WITH THE MODELS SUPPORTING IT ADVANCING THROUGH THE MIDWEST ON SAT AND DOWN ACROSS ESP THE LWR OH VLY ON SUN. WHILE SOME RELATIVELY MINOR DIFFERENCES EXIST AMONG THE GLOBAL MODELS...THERE IS RATHER GOOD AGREEMENT ON THE LARGER SCALE. THE 12Z UKMET IS SEEN AS BEING FASTER THAN THE GLOBAL MODEL CONSENSUS...WITH THE 12Z GEM AND 12Z ECMWF A TAD SLOWER. THE 12Z GFS AND 12Z NAM SPLIT THE DIFF BUT ARE JUST A LITTLE FASTER THAN THE GEM/ECMWF SOLNS. THE UKMET IS REALLY THE OUTLIER SOLN...SO WILL PREFER A NON-UKMET CONSENSUS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ORRISON