MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1147 AM EST WED MAR 05 2014 VALID MAR 05/1200 UTC THRU MAR 09/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 12Z NAM/GFS ALONG WITH PRELIMINARY PREFERENCES/FORECAST CONFIDENCE... THERE DID NOT APPEAR TO BE ANY INITIALIZATION ERRORS WITH THE 12Z NAM/GFS DEEMED SIGNIFICANT ENOUGH TO IMPACT THEIR FORECASTS. ...MIXED ARRAY OF SHORTWAVES EXITING THE SOUTHEASTERN U.S. COAST THIS EVENING... PRELIMINARY PREFERENCE: GENERAL MODEL CONSENSUS FORECAST CONFIDENCE: HIGH A BROAD AXIS OF DISORGANIZED SHORTWAVES ARE CURRENTLY SEEN ON WATER VAPOR IMAGERY NEARING THE SOUTHEASTERN U.S. COAST. THIS SYSTEM AND ITS ASSOCIATED BATCH OF LIGHT PRECIPITATION SHOULD EXIT OFFSHORE BY THIS EVENING WITH HEIGHTS BRIEFLY BUILDING IN THE WAKE. MODELS ARE IN GOOD AGREEMENT DURING THE BRIEF PERIOD THIS BATCH OF ENERGY IS OVER LAND. THUS...WILL RECOMMEND A GENERAL MODEL CONSENSUS AS ANY PIECE OF GUIDANCE SHOULD WORK WELL. ...UPPER TROF SLIDING THROUGH NEW ENGLAND BY 06/0000Z... PRELIMINARY PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: ABOVE AVERAGE A STRONG LOBE OF VORTICITY IS FORECAST TO SWING FROM SOUTHEASTERN ONTARIO THROUGH NEW ENGLAND LATER THIS EVENING. A REINFORCEMENT OF COLD AIR WILL ACCOMPANY THIS SYSTEM WITH NO PRECIPITATION GIVEN THE BUILDING HIGH PRESSURE AT THE SURFACE. SMALL-SCALE DIFFERENCES ARE NOTED BUT MOST OF THESE IMPACTS ARE WHEN THE SHORTWAVE IS EAST OF NEW ENGLAND. A GENERAL MODEL COMPROMISE WILL SUFFICE TO AVERAGE OUT ANY MINOR DIFFERENCES WHICH ARISE. ...PRONOUNCED SYSTEM CROSSING THE DEEP SOUTH THURSDAY/FRIDAY... ...PAIR OF SURFACE LOWS AFFECTING THE GULF OF MEXICO/SOUTHEASTERN U.S. COAST... PRELIMINARY PREFERENCE: BLEND OF THE 00Z ECMWF/UKMET FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE SHORTWAVES CURRENTLY MIGRATING THROUGH THE SOUTHERN HIGH PLAINS WILL EVENTUALLY TRANSITION INTO A MORE PRONOUNCED UPPER TROF WHILE ENTERING THE LOWER MS VALLEY/OZARKS BY EARLY THURSDAY. AS WAS THE CASE YESTERDAY...THE 12Z NAM IS SLOWER WITH THE EVOLUTION OF THIS SYSTEM ALONG THE GULF COAST WHICH PERSISTS THROUGHOUT THE SHORT RANGE PERIOD EXTENDING THROUGH 09/0000Z. THIS VERSION OF THE NAM IS EVEN SLOWER THAN THE 09Z SREF MEAN WHICH IS DEFINITELY THE SLOWEST AMONG THE ENSEMBLE MEANS. THE MULTI-DAY SPAGHETTI TRENDS SHOW A DEFINED SLOWING WHICH WOULD RULE OUT THE 00Z CMC AS IT CONTINUES TO BE TOO QUICK. THE 12Z GFS AND 00Z ECMWF/UKMET SEEM TO HAVE THE BEST HANDLE WITH THE CONTINUITY OF THE SYSTEM ALTHOUGH THE SLIGHTLY FASTER TREND IN THE 12Z GFS MAKES IT BRIEFLY PULL AWAY FROM THE CONSENSUS FORMED BY THE 06Z GEFS/00Z ECMWF ENSEMBLE MEANS. AT THE SURFACE...THE LOW TRACK OF THE 12Z NAM IS MUCH FURTHER WEST AS IT HUGS THE COAST WITH ONLY MODEST SUPPORT FROM THE 09Z SREF MEAN WHILE OTHER ENSEMBLE MEANS AND THEIR INDIVIDUAL MEMBERS ARE MUCH FURTHER OFFSHORE. A COMBINATION OF THE 00Z ECMWF/UKMET SEEMS TO BE THE BEST SOLUTION AT THIS AS IT SUPPORTS THE SLOWING TREND IN THE SPAGHETTIS AND FOLLOWS THE BETTER CLUSTERING SEEN IN THE ENSEMBLE LOW PLOTS. ...PACIFIC ENERGY ADVANCING INTO THE PACIFIC NORTHWEST/INTERMOUNTAIN WEST LATE THURSDAY... ...SYSTEM POTENTIALLY PINCHING OFF ACROSS THE FOUR CORNERS REGION LATE IN THE PERIOD... PRELIMINARY PREFERENCE: BLEND OF THE 00Z ECMWF/UKMET WITH THE 00Z ECMWF ENSEMBLE MEAN FORECAST CONFIDENCE: BELOW AVERAGE THE BROAD UPPER RIDGE INITIALLY CENTERED OVER THE INTERMOUNTAIN WEST WILL QUICKLY ADVANCE EASTWARD AHEAD OF A PROGRESSIVE AXIS OF HEIGHT FALLS. AS THE SYSTEM ADVANCES INLAND...THE LOW-AMPLITUDE FEATURE WILL SPREAD ACROSS MUCH OF THE INTERIOR MOUNTAIN WEST AND INTO THE CENTRAL/NORTHERN HIGH PLAINS. THE BIGGEST QUESTION IS HOW MUCH OF THE ENERGY WILL EVENTUALLY PEEL OFF TOWARD THE SOUTHWEST WHERE IT MAY CLOSE OFF VERSUS THE REMAINDER OF THE TROF SLIDING INTO THE MO VALLEY LATER ON. THROUGH 08/0000Z...THE 12Z NAM AND 00Z ECMWF/UKMET ARE IN ONE CAMP WHILE THE 12Z GFS BRINGS MORE ENERGY OFF TOWARD THE SOUTH AND WEST. MEANWHILE...THE 00Z CMC IS QUITE SLOW WITH THE PROGRESSION OF THE LONGWAVE TROF. THEREAFTER...MODELS BEGIN TO FURTHER DISAGREE WITH ONE ANOTHER AS THE PAIR OF SHORTWAVES BEGIN TO SPLIT AWAY FROM EACH OTHER. CONSIDERING MODEL TRENDS...THE PAST 5 CYCLES OF THE GFS KEEP SHIFTING TOWARD A MORE SEPARATED SYSTEM IN THE FOUR CORNERS REGION WHILE THE ECMWF HAS GRADUALLY MOVED IN OTHER DIRECTION AWAY FROM WHAT THE GFS SUGGESTS. 564-DM SPAGHETTI CONTOURS SHOW THE BEST CLUSTERING ACROSS THE SOUTHERN HIGH PLAINS WHICH GENERALLY FOLLOWS THE IDEA OF THE 00Z UKMET/ECMWF/ECMWF ENSEMBLE MEAN. FOR THIS PREFERENCE...WILL LEAN ON THAT COMBINATION WITH FUTURE CHANGES BASED ON ADDITIONAL 12Z GUIDANCE. ...NEXT BATCH OF COLD AIR DIVING INTO THE NORTHERN TIER OF THE COUNTRY BY THURSDAY... PRELIMINARY PREFERENCE: BLEND OF THE 12Z NAM/GFS WITH THE 00Z ECMWF FORECAST CONFIDENCE: AVERAGE A STRONG UPPER LOW INITIALLY CENTERED OVER NORTHERN ALBERTA WILL MOVE EASTWARD IN TIME TOWARD CENTRAL CANADA. AS THIS OCCURS...A POSITIVELY-TILTED TROF IS EXPECTED TO NOSE SOUTHWARD WHILE GRAZING THE ND/MN BORDER BY MIDDAY FRIDAY. THE 00Z CMC/UKMET ARE MUCH QUICKER WITH EJECTING THIS SYSTEM EASTWARD WHILE THE 12Z GFS HAS TRENDED SLOWER AWAY FROM ITS 06Z GEFS MEAN AND MORE TOWARD THE CLUSTERING OF THE 12Z NAM/00Z ECMWF. WPC WILL FAVOR SOME COMBINATION OF THE 12Z NAM/GFS WITH THE 00Z ECMWF WITH THIS SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER