MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 209 AM EST THU NOV 26 2015 VALID NOV 26/0000 UTC THRU NOV 29/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z 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 00Z/28 BLEND OF THE 00Z NAM/ECMWF AFTERWARD CONFIDENCE: SLIGHTLY BELOW AVERAGE IT SHOULD BE NOTED THAT THE 00Z UKMET IS THE CLOSEST OF THE NAM/GFS/ECMWF/UKMET/CMC TO THE 03Z NHC ADVISORY OF HURRICANE SANDRA AS IT SPLITS THE DIFFERENCE BETWEEN THE WESTERN 00Z ECMWF AND EASTERN 00Z GFS. PLEASE SEE RECENT ADVISORY 10 FROM NHC FOR FURTHER DETAILS. STRENGTHENING SWLY UPPER LEVEL FLOW SHOULD SHEAR THE CIRCULATION BUT ALSO PRESENT INCREASED TROPICAL MOISTURE ACROSS THE SOUTHERN PLAINS...PLEASE REFER TO QPFPFD FOR ADDITIONAL DETAILS. OVERALL EVOLUTION OF THE CLOSED UPPER LOW OVER THE GREAT BASIN APPEARS AGREEABLE THROUGH MUCH OF THE DETERMINISTIC AND ENSEMBLE MODEL SUITE UNTIL AOA 28/00Z. AFTERWARD...DIFFERENCES COMPOUND ON TWO FEATURES LEADING TO DIFFERENCES IN PLACEMENT AND ORIENTATION OF THE UPPER LOW ITSELF... THE FIRST AN UPSTREAM PACIFIC CUT-OFF LOW THAT DROPS SOUTHWEST THROUGH A WEAKNESS IN THE EASTERN PACIFIC RIDGING FRIDAY EVENING...THE SECOND IS THE MAGNITUDE OF THE INNER VORT ENERGY EJECTING OUT OF THE SOUTHWEST TOWARD THE CENTRAL ROCKIES FRIDAY EVENING INTO SATURDAY MORNING. THE ECMWF/UKMET MODELS HAVE BEEN THE MOST AGGRESSIVE WITH THE SECONDARY INFLUENCE WHICH ALLOWS FOR THE OVERALL TROF TO BECOME QUITE ELONGATED WSW TO ENE....WHILE THE GFS/CMC ARE BIT WEAKER AND ROTATE MORE ENERGY BACK NORTHWESTWARD INTO MT ALLOWING THE OVERALL ORIENTATION TO BE MORE CONCENTRIC. THE 00Z NAM FALLS IN BETWEEN. THE INFLUENCE FROM THE UPSTREAM PACIFIC CUT-OFF LOW BEGIN TO AFFECT THE TIMING/EVOLUTION... THE 00Z GFS WAS MOST DRAMATIC ...SHEDDING ONLY ABOUT HALF OF THE PACIFIC LOW'S ENERGY INTO THE SOUTHERN STREAM...MAKING IT SMALLER/MORE COMPACT AND AS SUCH MUCH FASTER SWINGING THROUGH TO THE AZ/NM BOARDER BY 29/12Z. THE CMC/NAM DEVELOPED SIMILARLY AND OF SIMILAR TIMING WITH THE CMC TUCKED A BIT CLOSER TO THE UPPER LOW ITSELF BY THE END OF THE FORECAST PERIOD. THE UKMET AND ECMWF STARTED OFF THE SLOWEST BUT THE UKMET OUTPACED THE ECMWF IN LINE WITH ITS BIAS TO HAVE SIMILAR TIMING TO THE CMC/NAM BY THE END OF THE PERIOD. THIS LEFT THE ECMWF SLOWEST STILL BACK OVER S CA. STILL THE ECMWF HAS BEEN GENERALLY CONSISTENT PARTICULARLY SINCE IT HAS SHIFTED A BIT WESTWARD AND LESS AGGRESSIVE WITH THE EJECTION OF THE LEADING WAVE INTO THE NORTH CENTRAL PLAINS BY SUNDAY MORNING...AND IS IN BETTER AGREEMENT WITH THE 12Z ECENS MEAN. OVERALL THE 00Z NAM APPEARED TO BE MOST MIDDLE GROUND THOUGH SLIGHTLY FAVORING THE ORIENTATION OF THE UKMET/ECMWF. AS SUCH THE PREFERENCE IS TOWARD THE 12Z ECENS MEAN/CMCE MEAN AND 18Z GEFS STILL... WHICH NOW CONTINUES TO BE REPRESENTED BY THE 00Z NAM AND NOW THE 00Z ECMWF. OVERALL SPREAD REMAINS HIGH AND SO CONFIDENCE REMAINS LOW IN EXACT EVOLUTION AFTER 28/00Z. AS SUCH CONFIDENCE REMAINS SLIGHTLY BELOW AVERAGE. COLD FRONT ACROSS THE GREAT LAKES & INTO THE NORTHEAST BY FRI NIGHT WEAK SURFACE WAVE ACROSS THE CNTRL GREAT LAKES THU/THU NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-GFS BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS ARE IN FAIRLY GOOD AGREEMENT ON THE POSITIONING/TIMING OF THE EASTWARD PROGRESSION OF THE SURFACE COLD FRONT ACROSS THE GREAT LAKES INTO THE NORTHEAST BY FRIDAY NIGHT. THE 00Z NAM HAS INCREASED PACE AND IS IN LINE WITH WITH THE EARLIER FAVORED 12Z ECMWF WHICH HAS REMAINED CONSISTENT WITH THE NEWER INTEGRATION (00Z RUN). THE 00Z UKMET AND 00Z CMC REMAIN A BIT SLOWER THAN THE 00Z NAM/ECMWF BUT CONTINUE TO EDGE INTO CLOSER AGREEMENT TO CONTINUE SUPPORT WITHIN THE PREFERRED BLEND. THE 00Z GFS HAS TRENDED FASTER THAN THE OTHER DETERMINISTIC MODELS...BACK TOWARD YESTERDAY'S *25/00Z* RUN. THIS DID NOT HAVE MUCH ENSEMBLE SUPPORT AND AS SUCH A NON-GFS BLEND IS PREFERRED...WITH HIGHER WEIGHTING TO THE SLIGHTLY FASTER 00Z ECMWF/NAM WHICH HAVE THE STRONGER ENSEMBLE SUPPORT. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA