MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1210 AM EDT THU SEP 01 2016 VALID SEP 01/0000 UTC THRU SEP 04/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING PREFERENCES AND FORECAST CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ UPPER LEVEL TROUGH ACROSS THE EASTERN U.S WITH ATTENDANT COLD FRONT PROGRESSION SHIFTS OFFSHORE BY FRIDAY NIGHT/SAT MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-NAM BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE STRONG MODEL AGREEMENT CONTINUES AS THE UL CYCLONE OVER SE CANADA BEGINS TO ELONGATE INTO A POSITIVE TILT TROF AS SHORTWAVE ENERGY DIVES THROUGH THE GREAT LAKES EARLY THIS MORNING SWINGING TROF ACROSS THE UPPER MID-ATLANTIC AND THRU NEW ENGLAND OFF SHORE BY SAT MORNING. THE 00Z NAM CONTINUES TO BE THE DISSENTING MODEL WITH A DEEPER SOLUTION FAIRLY TYPICAL OF ITS BIAS LAGGING/LINGERING THROUGH THE MID-ATLANTIC. ALL MODELS ALSO SUPPORT THE NOTION OF SHEDDING THE FAR SW PORTION OF THE TROF INTO THE OHIO RIVER VALLEY LEADING TO SOME BINARY INTERACTION WITH THE CYCLONIC ENVELOPE OF TROPICAL CYCLONE HERMINE AS IT LIFTS NORTH THROUGH THE CAROLINAS SAT/SUN. OVERALL A NON-NAM BLEND SEEMS TO FIT BEST WITH THE EVOLUTION OF THE TROF AND ASSOCIATED FRONTAL ZONE INCLUDING THE TIMING/PLACEMENT AND STRENGTH OF THE ENERGY IN THE OHIO VALLEY TO HAVE FAIRLY SOLID CONFIDENCE IN THIS BLEND (SLIGHTLY ABOVE AVERAGE). UPPER LOW/TROUGH DIGGING SOUTH OFFSHORE BRITISH COLUMBIA WITH HEIGHT FALLS ADVANCING ACROSS THE NORTHWEST THROUGH FRI/SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-UKMET BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE FAIRLY ROBUST LOW OFF THE BRITISH COLUMBIA COAST LINE WILL CONTINUE TO WOBBLE EASTWARD WITH ENERGY CARVING OUT THE BASE OF THE TROF INTO THE PACIFIC NORTHWEST BY FRIDAY MORNING UNDER FAIRLY STRONG CONSENSUS. AS THIS WAVE EJECTS NORTHEAST MODEL SPREAD BEGINS TO MANIFEST AS THE CLOSED LOW PIVOTS ON THE NW PERIPHERY OF THE RIDGE IN CENTRAL CANADA AND A NEW WAVE OUT OF THE EASTERN PANHANDLE OF ALASKA DESCENDS TO REINFORCE THE LARGER SCALE TROF IN THE NORTHWEST BY SUNDAY MORNING. THE 12Z UKMET BECOMES A FAST AND DISTINCT OUTLIER OF REST OF THE GUIDANCE PARTICULARLY ACROSS SASKATCHEWAN INCLUDING THE RESULTING SURFACE LOW; THOUGH THE N-S LEE TROF REMAINS AGREED UPON THROUGH MT/DAKOTAS GIVEN REMAINING UPSTREAM HEIGHT FALLS. THE 12Z ECMWF APPEARS TO BE A STRONGER SOLUTION WITHIN ITS OWN ENSEMBLE SUITE BUT HAS SOLID SUPPORT OF THE 12Z CMC AND THE 00Z NAM...WHILE ITS 12Z ECENS MEAN WAS FURTHER EAST TOWARD A SLIGHTLY WEAKER AND THEREFORE FASTER 00Z GFS. THOUGH THE TREND IN THE 00Z GFS WAS FURTHER WEST/STRONGER STRENGTHENING CONSENSUS. STRONG AGREEMENT CONTINUES WITH THE NON-UKMET SUITE WITH THE WAVE DESCENDING OUT OF BC BY SUNDAY AS WELL. AS SUCH A NON-UKMET BLEND IS PREFERRED WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE GIVEN MINOR DIFFERENCES WITH THE FASTER/WEAKER ENSEMBLES AND 00Z GFS AND THE DEEPER ECMWF/NAM/CMC -- RESULTING IN A NICE MIDDLE GROUND/HIGHER LIKELIHOOD BLEND. WEAK SURFACE WAVE ALONG THE SOUTHEAST COAST LIFTING INTO NW ATLANTIC IN WAKE OF T.D. EIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS/NAM AND 12Z ECMWF BLEND CONFIDENCE: AVERAGE SURFACE ANALYSIS INDICATES A WEAK SURFACE WAVE DEVELOPING ALONG THE SC COAST ATTM...AND MODELS GENERALLY SUPPORT MAINTAINING THIS WEAK REFLECTION WITHIN THE BROADER SW-NE TROF BETWEEN TROPICAL CYCLONE HERMINE AND TROPICAL DEPRESSION EIGHT AS IT (LIKE TD8) WILL LIFT NORTHEASTWARD THROUGH THE NW ATLANTIC. THE 12Z UKMET LAGS THE BEST SURFACE CLUSTER WITHIN THE ENSEMBLE PLOT AND REMAINS THERE THROUGHOUT ITS EVOLUTION...THE 12Z CMC IS WELL TIMED WITH THE CLUSTER BUT BY FRIDAY MORNING BECOMES A FASTER AND DEEPER SOLUTION. THE 00Z NAM/21Z SREF MATCHES THE 12Z ECMWF/ECENS MEANS QUITE WELL. THE 18Z GEFS AND 00Z GFS WERE A BIT WEAKER AND JUST A SHADE FASTER BUT ONLY IN A MINOR SENSE; AS SUCH WILL KEEP A 00Z NAM/GFS AND 12Z ECMWF BLEND AT AVERAGE CONFIDENCE. T.D. EIGHT MOVING OFF THE MID-ATLANTIC COAST INTO THE NW ATLANTIC ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: PLEASE REFER TO LATEST NHC FORECAST ADVISORY TROPICAL DEPRESSION 8 WILL CONTINUE TO MOVE AWAY FROM THE EAST COAST...WITH THE PREFERENCE IN LINE WITH A BLEND OF THE GLOBAL MODEL CONSENSUS ABOUT HALFWAY BETWEEN THE TWO CLUSTERS... THE 00Z GFS/GEFS/ECENS MEAN TO THE NORTHEAST AND THE UKMET/NAM TO THE SOUTHEAST AND THE ECMWF A BIT MORE ELONGATED INDICATIVE OF THE WEAKENING NATURE OF THE SURFACE REFLECTION. TROPICAL STORM HERMINE ~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: PLEASE REFER TO LATEST NHC FORECAST ADVISORY NHC TRACK FORECAST IS SLIGHTLY WEST OF THE BEST MATCH WITH THE 18Z GFS/GEFS AND 12Z ECWMF/ECENS MEAN BUT MATCHES WELL WITH THESE SOLUTIONS. THE 00Z NAM DUE TO A STRONGER/DEEPER TROF INTO THE OHIO VALLEY AND MID-ATLANTIC REMAINS A BIT FURTHER DEPRESSED SOUTH AND EAST EVENTUALLY MUCH DEEPER THAN MUCH OF THE GUIDANCE SUGGESTS AS THE SYSTEM GOES THROUGH EXTRATROPICAL TRANSITION... THE 00Z GFS HAS TRENDED A BIT FASTER AND THEREFORE A BIT FURTHER EAST...YET PIVOTS TOWARD THE NORTHERN STREAM ENERGY IN THE OHIO VALLEY BY SUNDAY JUST LESSER SO THAN ITS PRIOR 18Z RUN BRINGING IT CLOSER TO THE 12Z UKMET AT LEAST LONGITUDINALLY. === GALLINA www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml...