MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 222 PM EST THU NOV 26 2015 VALID NOV 26/1200 UTC THRU NOV 30/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING FORECAST PREFERENCES AND CONFIDENCE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ CLOSED LOW MOVING OVER THE GREAT BASIN - PACIFIC CLOSED LOW SHEARING INTO THE GREAT BASIN LOW DEVELOPING REX BLOCK ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: OPERATIONAL MODEL BLEND THROUGH 28/00Z 26/12Z ECMWF AFTERWARD CONFIDENCE: BELOW AVERAGE IT SHOULD BE NOTED THAT THE 12Z NAM/GFS/ECMWF/UKMET/CMC WERE CLOSE TO THE 15Z NHC ADVISORY OF HURRICANE SANDRA THROUGH 27/12Z. AFTER THAT...THE 12Z UKMET AND GFS WERE THE CLOSEST SINCE THEY TENDED TO BE ON THE EASTERN SIDE OF THE GUIDANCE ENVELOPE. PLEASE SEE THE LATEST ADVISORY 10 FROM NHC FOR FURTHER DETAILS. THE 12Z NCEP RUNS AND THE UKMET WERE IN FAIRLY GOOD AGREEMENT IN DEPICTING THE EVOLUTION OF THE CLOSED UPPER LOW OVER THE GREAT BASIN THROUGH 28/00Z...AFTER WHICH TIME DIFFERENCES IN HOW MODELS HANDLE THE PLACEMENT OF THE UPPER LOW AND THE MAGNITUDE OF THE VORT ENERGY EJECTING OUT OF THE SOUTHWEST U.S. TOWARDS THE CENTRAL ROCKIES BY SATURDAY MORNING AND OVER THE PLAINS LATER IN THE DAY. THE 12Z ECMWF STILL HAD ENERGY ROTATING AROUND THE LOW WHICH ELONGATES THE SYSTEM...ALTHOUGH IT NOW WAS WEAKER THAN THE NCEP RUNS OR THE UKMET. THE CANADIAN WAS NOT SIGNIFICANTLY DIFFERENT THAN THE ECMWF THOUGH IT WAS A HAIR STRONGER THAN THE ECMWF BY 29/18Z. THE UPSTREAM PACIFIC CUT-OFF LOW ALSO IMPACTS THE TIMING AND EVOLUTION OF THE CLOSED LOW. THE 12Z GFS WAS EVEN MORE DRAMATIC THAN ITS 26/00Z RUN...SHEDDING ONLY ABOUT HALF OF THE PACIFIC LOW'S ENERGY INTO THE SOUTHERN STREAM. MOST MODELS ARE IN AGREEMENT THAT AT LEAST SOME ENERGY WILL ROTATE AROUND THE WESTERN AND SOUTHERN SIDE OF THE LOW AND EVENTUALLY OVER THE SOUTHERN GREAT BASIN. THE ECMWF REMAINED ON THE SLOWER SIDE OF THE GUIDANCE...A CONSISTENT SIGNAL THAT THE ECMWF HAS BEEN SENDING FOR MULTIPLE RUNS. NO CLEAR SIGNAL FROM THE ENSEMBLES SINCE THE ENSEMBLE MEANS TEND TO SUPPORT THEIR RESPECTIVE OPERATIONAL RUNS...SO WE ARE INCLINED TO KEEP AN BLEND OF THE ECMWF/NCEP RUNS TO CAPTURE THE CONSISTENCY OF THE ECMWF POSN WHILE ALLOWING FOR A LITTLE MORE ENERGY TO ROTATE AROUND THE NORTH SIDE OF THE LOW AND THE SECOND PIECE OF ENERGY ROUNDING THE WESTERN/SOUTHERN SIDE OF THE LOW. COLD FRONT ACROSS THE GREAT LAKES & INTO THE NORTHEAST BY FRI NIGHT WEAK SURFACE WAVE ACROSS THE CNTRL GREAT LAKES THU/THU NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: ECMWF/NAM CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE 12Z NCEP MODELS AND THE 12Z RUN OF THE UKMET WERE REMAINED IN PRETTY GOOD AGREEMENT WITH EACH OTHER AND WITH CONTINUITY...ALTHOUGH IF ANYTHING THE 12Z GFS SPED UP RELTIVE TO ITS 26/00Z RUN. THE NAM ROUGLY MAINTAINED THE SAME RELATIVE POSITION WITHIN THE SPREAD OF THE 00Z MODELS AND ENSEMBLES. THE UKMET LOOKED TO BE A DEEP/SLOW OUTLIER. THE MODEL ENSEMBLE MEAN STILL GIVE MORE WEIGHT TO THE ECMWF/NAM SOLN. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... BANN