MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 232 AM EDT WED SEP 10 2014 VALID SEP 10/0000 UTC THRU SEP 13/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION...INCLUDING FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ SURFACE LOW CURRENTLY OFF THE DELMARVA PENINSULA...FORECAST TO DISSIPATE NWD OFF OF THE NEW ENGLAND COAST LATE THU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM/GFS/ECMWF BLEND CONFIDENCE: ABOVE AVERAGE THE 00Z CMC/UKMET DEVIATE FROM THE REMAINING DETERMINISTIC/ENSEMBLE CONSENSUS IN BEING DISPLACED TO THE EAST WITH THIS LOW. THE CMC IS ALSO STRONGEST BUT HAS HAD A POOR HISTORY IN FORECASTING THIS SYSTEM SO FAR THIS WEEK. THE PREFERENCE IS TO STAY CLOSE TO THE CONSISTENT ENSEMBLE MEANS WHICH AGREE WITH THE 00Z NAM/GFS/ECMWF. SURFACE LOW LIFTING THROUGH THE GREAT LAKES LATER TODAY AND ITS TRAILING COLD FRONT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z NAM...00Z GFS...00Z ECMWF BLEND CONFIDENCE: ABOVE AVERAGE THE 00Z NAM HAS COME INTO BETTER ALIGNMENT WITH THE REMAINING MODELS...ALONG WITH THE PLACEMENT OF THE 00Z UKMET/CMC COMPARED TO THE PREFERENCE LISTED ABOVE. WHILE THE 00Z GFS REMAINS A BIT STRONGER WITH THE CORRESPONDING MID-LEVEL SHORTWAVE IN QUEBEC THU EVENING...THE ENSEMBLE MEANS SUPPORT AN UPPER WAVE / SURFACE LOW NEAR OR STRONGER THAN THE NAM/ECMWF. THE 00Z UKMET/CMC HAVE IN FACT TRENDED EVEN STRONGER THAN THE GFS WITH THE SURFACE LOW TRACKING THROUGH QUEBEC. HOWEVER...GIVEN THEIR LESS CONSISTENT NATURE AND THE FACT THAT THE ECMWF HAS MAINTAINED STRENGTH/POSITION CONTINUITY HERE...BLENDING THE POSITION/STRENGTH OF THE NAM/GFS/ECMWF SHOULD ALLOW FOR A DECENT COMPROMISE FOR THIS SYSTEM. SHORTWAVE TRACKING FROM THE NRN ROCKIES TO THE GREAT LAKES BY SAT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z NAM...00Z ECMWF CONFIDENCE: AVERAGE THERE IS REASONABLE AGREEMENT UNTIL FRI...WHEN THE 00Z GFS SEEMS LIKE IT COULD BE A LITTLE TOO FAST WITH THE UPPER WAVE TRACKING ACROSS THE N-CNTRL U.S. GIVEN ITS TROUGH AXIS PLACED ABOUT 100-150 MILES EAST OF THE AXIS OF THE ENSEMBLE MEANS BY 12Z/13...SAT MORNING. THE GFS HAS SLOWED FROM ITS 12Z/09 RUN...BUT THERE IS BETTER SUPPORT FOR A SLOWER WAVE...WITH SOME AMPLIFICATION....SIMILAR TO A BLEND OF THE 00Z NAM AND 00Z ECMWF. THE NAM COULD BE TOO SLOW...BUT TRENDS AND THE CURRENT DISTRIBUTION OF GUIDANCE ARGUES FOR A LITTLE SLOWER THAN THE 00Z GFS...WITH SUPPORT FROM THE 00Z UKMET. THE 00Z CMC ALSO APPEARS A BIT FAST BY SAT MORNING OVER THE GREAT LAKES. WEAK MID-UPPER WAVE TRACKING THROUGH THE GULF OF MEXICO...REACHING SOUTH TEXAS THU NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 00Z NAM BLEND CONFIDENCE: AVERAGE RUN TO RUN CONSISTENCY...MODEL SPREAD AND TRENDS SUPPORT A 00Z GFS/12Z ECMWF COMPROMISE. THE 00Z CMC HAS COME IN STRONGER THAN ITS LIKELY WEAK 12Z RUN...AND THE 00Z UKMET HAS MADE ONLY MINOR ADJUSTMENTS FROM ITS 12Z RUN. THIS ALL MAKES THE 00Z NAM APPEAR TOO STRONG AND FAST...WITH A NON-00Z NAM COMPROMISE OF GUIDANCE PREFERRED. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO