MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1249 PM EDT FRI JUN 27 2014 VALID JUN 27/1200 UTC THRU JUL 01/0000 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. ...CENTRAL U.S. LONGWAVE TROF... ...DEVELOPMENT OF CLOSED LOW ACROSS SOUTHERN MANITOBA BY SUNDAY... ...MIGRATORY BAROCLINIC ZONE... PRELIMINARY PREFERENCE: BLEND OF THE 00Z ECMWF WITH THE 06Z GEFS/00Z ECMWF ENSEMBLE MEANS FORECAST CONFIDENCE: BELOW AVERAGE AN ANOMALOUSLY STRONG UPPER TROF ACROSS THE WESTERN U.S. WILL TRANSLATE EASTWARD DURING THE NEXT COUPLE OF DAYS. MESOSCALE IMPULSES WITHIN THE BROADER CYCLONIC FLOW WILL PROVIDE FOCI FOR DAILY ROUNDS OF CONVECTION ACROSS THE GREAT PLAINS/MS VALLEY. UPSTREAM ENERGY FROM THE PACIFIC TROF WILL HELP THE SYSTEM GATHER STRENGTH AND EVENTUALLY LEAD TO THE DEVELOPMENT OF A CLOSED LOW ACROSS SOUTH-CENTRAL CANADA. THE 12Z GFS CARRIES THE CORE OF THE LOWER HEIGHTS TOWARD THE ND/MN BORDER BY 30/0000Z WITH OTHER MODELS KEEPING THESE HEIGHTS FURTHER TO THE NORTH. ULTIMATELY THE 06Z GEFS/00Z ECMWF ENSEMBLE MEANS ARE NOT TERRIBLY DIFFERENT FROM ONE ANOTHER BUT HAVE A FEELING THE NEWER GEFS WILL FOLLOW THE SOUTHWARD TREND IN THE 12Z GFS. THE 00Z ECMWF FOLLOWS THIS PAIR OF MEANS REASONABLY SO WILL PREFER A COMBINATION OF THESE MODELS WITH CONFIDENCE NOT TERRIBLY HIGH. ...MID-LEVEL WEAKNESS AFFECTING THE WESTERN/CENTRAL GULF COAST... PRELIMINARY PREFERENCE: NON-12Z NAM MODEL COMPROMISE FORECAST CONFIDENCE: AVERAGE A WEAKNESS NOTED IN THE 500-MB RIDGE ACROSS THE WESTERN GULF OF MEXICO WILL SET A FOCUS FOR SHOWERS AND THUNDERSTORMS THE NEXT COUPLE OF DAYS OVER THE WESTERN/CENTRAL GULF COAST. WHILE THE MODELS GENERALLY AGREE ON THE FIRST IMPULSE MOVING INLAND ON DAY 1...THE 12Z NAM IS MUCH MORE EMPHATIC ABOUT THE DEVELOPMENT OF A SECOND WAVE BY THE FOLLOWING DAY. SEE VERY LITTLE SUPPORT FOR THIS SOLUTION SO WILL LEAN TOWARD A NON-12Z NAM MODEL COMPROMISE. ...LINGERING SURFACE LOW OFF THE SOUTHEASTERN U.S. COAST... PRELIMINARY PREFERENCE: BLEND OF THE 12Z GFS/06Z GEFS MEAN FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE AS OF THIS MORNING...SURFACE OBSERVATIONS IN THE VICINITY OF THE NC/SC BORDER DEPICTED A WEAK AREA OF LOW PRESSURE WHICH WAS ATTACHED TO A STATIONARY FRONTAL ZONE. THIS SURFACE WAVE IS EXPECTED TO DRIFT SOUTH IN TIME BEFORE DRIFTING OFFSHORE BY SATURDAY. LATE IN THE WEEKEND THERE IS MORE VARIANCE NOTED IN THE MODELS WITH REGARD TO PLACEMENT. BY 29/1200Z...THE 00Z UKMET IS SQUASHED FURTHER TOWARD THE SOUTH WHILE THE 00Z CMC MOVES THE SYSTEM A LITTLE MORE UP THE COAST. TOWARD THE END OF THE PERIOD WITH 12Z NAM/GFS AND 09Z SREF MEAN ARE PLACED OFF THE EASTERN FL COAST WITH THE INDIVIDUAL 00Z GEFS MEMBERS AGREEING WITH THIS SOLUTION. MEANWHILE THE 00Z ECMWF/ECMWF ENSEMBLE MEAN ARE OFF TO THE NORTHEAST WITH THE MEMBERS EXHIBITING MORE ENSEMBLE SPREAD. WILL FAVOR THE IDEA THE GEFS MEAN PORTRAYS AS ITS MEMBERS CONTAIN LESS SPREAD AND APPEAR REASONABLY CLOSE TO THE 12Z ENSEMBLE. ...MEAN UPPER CYCLONE AFFECTING THE NORTHEASTERN PACIFIC... PRELIMINARY PREFERENCE: BLEND OF THE 12Z GFS/00Z ECMWF FORECAST CONFIDENCE: SLIGHTLY BELOW AVERAGE BROAD CYCLONIC FLOW ANCHORING THE NORTHEASTERN PACIFIC WILL SLOWLY MIGRATE EASTWARD WITH THE CLOSED CENTER NEARING THE BRITISH COLUMBIA COAST BY LATER IN THE WEEKEND. GENERAL WEST-NORTHWESTERLY FLOW SHOULD PERSIST INTO THE PACIFIC NORTHWEST/UPPER INTERMOUNTAIN WEST WITH THE ENERGY EVENTUALLY HELPING ESTABLISH/MAINTAIN THE CENTRAL U.S. TROF. BY EARLY NEXT WEEK THE SYSTEM WASHES OUT AS ADDITIONAL PACIFIC MOISTURE MOVES IN FROM THE WEST. THIS SCENARIO WILL FAVOR GRADUAL BUILDING OF HEIGHTS ACROSS THE PACIFIC COAST WITH A RATHER AMPLIFIED SETUP UNFOLDING ENTERING THE NEXT CALENDAR MONTH. WHILE THIS FEATURE DOES NOT AFFECT THE CONUS THROUGH 84 HOURS...THERE IS A GREAT DEAL OF UNCERTAINTY WITH THE NORTHEASTERN PACIFIC UPPER LOW. THE 12Z NAM/GFS ALONG WITH THE 06Z GEFS/09Z SREF MEANS ARE QUICKER RELATIVE TO THE MORE WESTWARD PLACED 00Z CMC/ECMWF/ECMWF ENSEMBLE MEAN. SUCH SPREAD IS CONSISTENT WITH THE RESPECTIVE SPAGHETTI PLOTS AS WELL. UNTIL THE FORECAST BECOMES BETTER RESOLVED...WITH FAVOR A BLEND OF THE TWO IDEAS. ...WEAKLY DEFINED UPPER TROF DEPARTING NEW ENGLAND ON FRIDAY... PRELIMINARY PREFERENCE: GENERAL MODEL CONSENSUS FORECAST CONFIDENCE: HIGH EARLY IN THE FORECAST A WEAK UPPER TROF WILL EXIST THE NORTHEASTERN U.S. WITH LITTLE DIFFERENCES NOTED IN THE GUIDANCE. A GENERAL MODEL CONSENSUS WILL SUFFICE HERE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER