MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 145 PM 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 CMC/UKMET/ECMWF ALONG WITH FINAL 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... FINAL 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 SHORT 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... FINAL 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... FINAL PREFERENCE: BLEND OF THE 12Z UKMET WITH THE 00Z ECMWF/ECMWF ENSEMBLE MEAN 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 12Z/00Z CMC AS THEY CONTINUE TO BE TOO QUICK. THE 12Z GFS/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 12Z 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. THE LATEST 12Z ECMWF HAS MADE A SHIFT TOWARD THE COAST WITH ITS LOW TRACK WHICH ENDS UP BEING A BIT WEST OF THE STRONGER CONSENSUS VISIBLE IN THE ENSEMBLE LOW PLOTS. PREFER THE COMBINATION OF THE 12Z UKMET WITH THE FORMER 00Z ECMWF/ECMWF ENSEMBLE MEAN AND LEAVE OUT THE MORE COASTAL 12Z ECMWF. OVERALL...THIS SOLUTION STILL SUPPORTS THE SLOWING TREND IN THE SPAGHETTIS AND ALONG WITH THE BETTER CLUSTERING FROM 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... FINAL PREFERENCE: BLEND OF THE 12Z 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. IN GENERAL THE 12Z GFS STILL BRINGS MORE OF ITS ENERGY TOWARD THE SOUTH AND WEST VERSUS ANY OTHER MODEL. THE PAST 5 CYCLES OF THE GFS SUGGEST THE SOLUTION HAS BEEN TRENDING TOWARD BEING MORE SOUTHWESTERN THAN PREVIOUS RUNS. MEANWHILE...THE 12Z ECMWF HAS NOW SHIFTED IN THE DIRECTION OF THE 12Z GFS BUT NOT AS AGGRESSIVELY. THE CHANGE IN THE 12Z ECMWF ALSO BRINGS ITS CLOSER TO THE 12Z/00Z UKMET WHICH DID NOT CHANGE SIGNIFICANTLY. OVERALL...564-DM SPAGHETTI CONTOURS SHOW THE BEST CLUSTERING ACROSS THE SOUTHERN HIGH PLAINS WHICH GENERALLY FOLLOWS THE IDEA OF THE 12Z ECMWF/UKMET AND 00Z ECMWF ENSEMBLE MEAN. FOR THIS PREFERENCE...WILL LEAN ON THAT COMBINATION AND STILL FOLLOW THE BELIEF THAT THE 12Z GFS IS TOO FAR WEST. ...NEXT BATCH OF COLD AIR DIVING INTO THE NORTHERN TIER OF THE COUNTRY BY THURSDAY... FINAL PREFERENCE: A NON-12Z UKMET SOLUTION 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 12Z/00Z 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/ECMWF. WPC WILL FAVOR A NON-12Z UKMET SOLUTION GIVEN ALL OF THE ABOVE. www.wpc.ncep.noaa.gov/html/model2.shtml... RUBIN-OSTER