MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 244 AM EDT SAT OCT 18 2014 VALID OCT 18/0000 UTC THRU OCT 21/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF ALL 00Z MODEL GUIDANCE ALONG WITH FINAL PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 00Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...LOBE OF ENERGY MOVING FROM THE GREAT LAKES TO INTERIOR NEW ENGLAND ON SATURDAY... FINAL PREFERENCE: GENERAL MODEL CONSENSUS FORECAST CONFIDENCE: HIGH A SHORTWAVE CURRENTLY CROSSING THE LOWER GREAT LAKES WILL EVENTUALLY MOVE INTO INTERIOR NEW ENGLAND BY 18/1800Z. MODEL DIFFERENCES DURING THIS SHORT PERIOD OF TIME ARE QUITE SMALL SO A GENERAL MODEL CONSENSUS SOLUTION IS RECOMMENDED. ...SECONDARY SHORTWAVE DIGGING INTO THE LOWER OH VALLEY BY SATURDAY EVENING... ...STRONG COLD FRONT EXITING THE EASTERN SEABOARD... FINAL PREFERENCE: BLEND OF THE 00Z NAM/ECMWF FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE A PRONOUNCED IMPULSE NOTED ON WATER VAPOR IMAGERY IS CURRENTLY CROSSING EXTREME NORTHERN MN. THIS SYSTEM IS FORECAST TO BE RATHER PROGRESSIVE IN NATURE REACHING THE LOWER OH VALLEY BY 19/0000Z. THERE ARE SOME SUBTLE MODEL DIFFERENCES AS THE WAVE EXITS THE VA CAPES EARLY SUNDAY MORNING WITH THE 00Z GFS SLIGHTLY AHEAD OF THE OTHER GUIDANCE. THIS HAS BEEN A TRAIT OF THE GFS IN RECENT DAYS. AFTER REVIEWING ALL OF THE AVAILABLE 00Z GUIDANCE...THE 00Z GFS REMAINS FASTER THAN THESE SOLUTIONS AS WELL. OVERALL...THE PAST FEW CYCLES OF THE ECMWF ENSEMBLE MEAN HAVE BEEN FAIRLY STABLE OF LATE WITH REGARD TO RUN-TO-RUN CONTINUITY. THE 00Z NAM/ECMWF SEEM TO GRASP THIS SOLUTION RATHER WELL SO WILL LEAN ON THIS COMBINATION HERE. ...CLIPPER-LIKE SYSTEM TRACKING FROM THE UPPER MIDWEST INTO THE NORTHEASTERN U.S... FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF FORECAST CONFIDENCE: AVERAGE WITH MID-LEVEL HEIGHTS GRADUALLY BUILDING OVER THE CENTER OF THE NATION BY MONDAY MORNING...A PRONOUNCED CLIPPER-LIKE SYSTEM IS EXPECTED TO SLIDE FROM THE UPPER GREAT LAKES INTO THE MID-ATLANTIC ON MONDAY/TUESDAY. THE 564-DM SPAGHETTI PLOTS SHOW SPREAD WHICH HAS SHOWN MUCH VARIABILITY DURING THE PAST FEW MODEL CYCLES. IN THE 12Z PLOTS FROM 10/17...THE 12Z GEFS MEMBERS ARE DECIDEDLY SLOWER WITH OTHER GUIDANCE LIKE THE 12Z ECMWF ENSEMBLE MEMBERS/UKMET ON THE FASTER SIDE. RELATIVE TO 24 HOURS AGO...THE ECMWF ENSEMBLE MEMBERS WERE THE ONES WHICH WERE SLOWER. WITH REGARD TO MORE RECENT GUIDANCE...THE 00Z GFS CAME IN LOOKING MORE LIKE THE 00Z ECMWF/12Z ECMWF ENSEMBLE MEAN WHICH ARE SLOWER THAN THE MORE PROGRESSIVE 00Z CMC/UKMET. GIVEN THIS ASSESSMENT...WILL FAVOR A BLEND OF THE 00Z GFS/ECMWF. ...SHEARING SHORTWAVE CROSSING THE FOUR CORNERS REGION EARLY SATURDAY... FINAL PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE AN UPPER LOW WHICH WAS INITIALLY CLOSED IN NATURE HAS OPENED UP AND HAS BEGUN SHEARING ACROSS SOUTHERN AZ. BY 19/0000Z...MODELS INDICATE A MYRIAD OF WEAK VORTICITY MAXIMA CROSSING THE CENTRAL ROCKIES/SOUTHERN HIGH PLAINS. THERE DOES NOT APPEAR TO BE ANY MEANINGFUL DIFFERENCES WITH THIS FEATURE SO WILL PROPOSE A GENERAL MODEL COMPROMISE. ...UPPER TROF REACHING THE WEST COAST BY 18/1200Z... ...SLOW-MOVING CLOSED LOW MOVING ACROSS NORTHERN MX... FINAL PREFERENCE: NON-00Z CMC MODEL COMPROMISE FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE A FULL-LATITUDE TROF APPROACHING THE WEST COAST IS WELL AGREED UPON IN ALL THE GUIDANCE. EVENTUALLY THE TROF SPLITS WITH THE NORTHERN STREAM CARRYING ENERGY PROGRESSIVELY THROUGH WESTERN/CENTRAL CANADA WHILE THE OTHER IMPULSE DIVES DOWN INTO THE SOUTHWESTERN U.S. THE SOUTHERN STREAM SYSTEM WILL CONSIST OF A SLOW-MOVING UPPER LOW WHICH IS FORECAST TO TRACK FROM NORTHERN BAJA CA TO FAR WEST TX BETWEEN 19/1200Z AND 21/1200Z. IT APPEARS THE 00Z/12Z CMC DIVERGE MOST SIGNIFICANTLY FROM THE MODEL CLUSTERING AS THEY ARE WEAKER ALOFT. THE PREFERENCE IS A NON-00Z CMC MODEL COMPROMISE. ...MEAN TROF AFFECTING THE WESTERN U.S. EARLY NEXT WEEK... ...ASSOCIATED PACIFIC FRONT MOVING INLAND... FINAL PREFERENCE: BLEND OF THE 00Z GFS/ECMWF FORECAST CONFIDENCE: SLIGHTLY ABOVE AVERAGE MODELS SHOW AN IMPRESSIVE UPPER TROF REACHING THE WEST COAST ON MONDAY WITH THE ENSEMBLE MEANS BEING NEARLY IN LINE WITH ONE ANOTHER. THE 00Z NAM/CMC SEEM TO BE QUICKER THAN THESE CLUSTERED MEANS AS THEY BOTH DRIVE SHORTWAVE ENERGY INTO THE CENTRAL GREAT BASIN BY TUESDAY MORNING. ENSEMBLES WOULD SUGGEST A COMBINATION OF THE 00Z GFS/ECMWF WOULD BE BEST TO HANDLE THE TIMING OF THIS EXPANSIVE UPPER TROF. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER