MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 238 PM EDT WED JUN 18 2014 VALID JUN 18/1200 UTC THRU JUN 22/0000 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. ...DEEP UPPER LOW INITIALLY OVER THE NORTHERN ROCKIES/UPPER INTERMOUNTAIN WEST... ...ASSOCIATED FRONTAL ZONE/SURFACE WAVES... FINAL PREFERENCE: BLEND OF THE 12Z GFS WITH THE 12Z GEFS/00Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE AN ANOMALOUS CLOSED LOW POSITIONED OVER THE NORTHERN ROCKIES/UPPER INTERMOUNTAIN WEST HAS CREATED QUITE AN AMPLIFIED PATTERN FOR THE MIDDLE OF JUNE. DURING THE NEXT 24 HOURS...THE CORE OF THE UPPER LOW IS FORECAST TO LIFT UP TOWARD THE ALBERTA/SASKATCHEWAN BORDER WHILE SHORTWAVES TRAVERSE TOWARD THE NORTHERN PLAINS/UPPER MIDWEST. AS THE CORE OF THE SYSTEM LIFTS INTO SOUTHERN MANITOBA BY 21/0000Z....THE MID-LEVEL FLOW BEGINS TO FLATTEN OUT CONSIDERABLY. THE 12Z NAM/09Z SREF MEAN KEEP PROJECTING THIS SYSTEM EASTWARD TOWARD WESTERN ONTARIO WHILE THE REMAINING GUIDANCE ALLOW IT TO BE CAPTURED BY A NORTHERN STREAM TROF TO THE WEST. THE LATTER SEEMS MORE PLAUSIBLE BASED ON SPAGHETTI PLOTS WITH QUITE A BIT OF VARIANCE NOTED IN THESE SOLUTIONS. MODELS RUN-TO-RUN CONTINUITY HAVE NOT BEEN GREAT WITH THE 12Z GFS BEING THE ONLY MODEL FOLLOWING MORE CLOSELY TO THE ENSEMBLE MEANS. WPC WILL FAVOR A BLEND OF THE 12Z GFS WITH THE 12Z GEFS/00Z ECMWF ENSEMBLE MEANS WITH CONFIDENCE REMAINING AT SLIGHTLY BELOW AVERAGE. ...INVERTED TROF LINGERING ACROSS FL... FINAL PREFERENCE: A NON-12Z NAM MODEL COMPROMISE FORECAST CONFIDENCE: AVERAGE A BROAD INVERTED TROF EXTENDING FROM CUBA UP ACROSS FL WILL CONTINUE TO PROVIDE A MID-LEVEL FOCUS FOR SHOWERS AND THUNDERSTORMS. ONE OF THE MORE DEFINED IMPULSES SHOULD EMERGE FROM THE BAHAMAS AND LIFT NORTH AND WEST ALONG THE EASTERN FL COAST. THE 12Z NAM IS A BIT QUICKER WITH THIS EVOLUTION WHILE THE 12Z GFS EVENTUALLY JOINS THE NAM SOLUTION BY 20/0000Z. THEREAFTER...MODELS PROVIDE SIMILAR SOLUTIONS ALTHOUGH THE FORECAST INVOLVES RELATIVELY SMALL SCALE FEATURES WHICH SEEM TO VARY FROM RUN TO RUN. GIVEN THE 12Z NAM APPEARED FAST EARLY ON...WILL FAVOR A NON-12Z NAM MODEL COMPROMISE WITH THE BLEND HOPEFULLY RESOLVING THE MESOSCALE DIFFERENCES. ...MID-LEVEL WEAKNESS AFFECTING THE SOUTHERN PLAINS BY FRIDAY... FINAL PREFERENCE: A NON-12Z/00Z CMC MODEL COMPROMISE FORECAST CONFIDENCE: AVERAGE SHORTWAVE ENERGY FROM SOUTHERN MEXICO WILL GRADUALLY ORGANIZE INTO A MORE DEFINED SYSTEM WHILE CROSSING THE RIO GRANDE BY LATE THURSDAY. THROUGH 20/1200Z...WITH THE EXCEPTION OF THE MORE SOUTHERN 12Z/00Z CMC...THE GUIDANCE DO AGREE ON THIS WEAKNESS BEING IN THE VICINITY OF THE BIG BEND ON FRIDAY MORNING. IN TIME...THE PROGRESSION OF THE SYSTEM VARIES WITH THE 12Z NAM/GFS FAVORING A MORE EASTERN POSITION WHILE THE 12Z ECMWF AND 00Z ECMWF ENSEMBLE/09Z SREF MEANS SUPPORT A MOVEMENT TOWARD THE WEST. OVERALL...A GENERAL MODEL COMPROMISE AMONG THE NON-12Z/00Z CMC SOLUTIONS SEEMS TO BE THE WAY TO GO HERE GIVEN THE INHERENT UNCERTAINTY IN THE EVOLUTION BEYOND 48 HOURS. ...MEAN UPPER TROF ANCHORING THE NORTHEAST PACIFIC/WESTERN CANADA... FINAL PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: AVERAGE WITH A CORE OF THE LOWER HEIGHTS REMAINING WELL TO THE NORTH...A SERIES OF SHORTWAVES WILL TRAVERSE AROUND THE BASE OF THE TROF THROUGHOUT THE PERIOD. ONE OF THE MORE POTENT IMPULSES SHOULD SLIDE TOWARD VANCOUVER ISLAND BY THURSDAY EVENING WITH DIFFERENCES BEING RATHER MINOR MOVING TOWARD EARLY FRIDAY. AS THE FLOW TURNS MORE ZONAL IN THE WAKE...THE LARGE SCALE DIFFERENCES ARE SMALL WITH MORE OF THE UNCERTAINTY WELL TO THE NORTH WITHIN THE CORE OF STRONGER HEIGHT FALLS. GIVEN THIS ASSESSMENT...WILL RECOMMEND A GENERAL MODEL COMPROMISE. ...BROAD CLOSED LOW SPINNING OVER NORTHEASTERN NORTH AMERICA... FINAL PREFERENCE: BLEND OF THE 12Z GEFS/00Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE THE BLOCKED HIGHER LATITUDE PATTERN IS EVIDENT WITH ANOTHER CLOSED LOW ANCHORING THE OTHER SIDE OF NORTH AMERICA. A BROAD MID-LEVEL VORTEX SHOULD BECOME A MAINSTAY FEATURE DURING THE SHORT RANGE AS IT ANCHORS NORTHEASTERN NORTH AMERICA. THERE IS A TIMING ISSUE NOTED WITH A PRONOUNCED SHORTWAVE TRACKING THROUGH UPPER NEW ENGLAND EARLY FRIDAY WITH THE 12Z NAM/GFS DECIDEDLY SLOWER THAN OTHER GUIDANCE INCLUDING MOST OF THE ENSEMBLE MEANS. THE 12Z ECMWF HAS COME IN ON THE OPPOSITE SIDE OF THE SPECTRUM BEING MORE PROGRESSIVE THAN ANY PIECE OF GUIDANCE. OVERALL THE SPREAD HAS SLIGHTLY INCREASED AFTER ASSESSING ALL OF THE RECENT MODEL RUNS SO WILL FEEL A COMBINATION OF THE ENSEMBLE MEANS WILL WORK BEST HERE WHILE MAINTAINING CONFIDENCE AT SOME LEVEL BELOW AVERAGE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER