MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 237 AM EDT SAT MAY 31 2014 VALID MAY 31/0000 UTC THRU JUN 03/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... ...AN EVALUATION OF THE 00Z CMC/UKMET/ECMWF 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. ...CLOSED LOW WEAKENING IN THE VICINITY OF THE ARKLATEX... FINAL PREFERENCE: GENERAL MODEL COMPROMISE FORECAST CONFIDENCE: AVERAGE A CLOSED LOW CURRENTLY SWIRLING OVER THE ARKLATEX HAS BEEN A FEATURE AFFECTING SOME PORTION OF THE CONUS FOR THE PAST 10 OR SO DAYS. THIS SYSTEM IS EXPECTED TO GRADUALLY DRIFT SOUTHWARD WHILE SLOWLY BECOMING MORE ILL-DEFINED LATER THIS WEEKEND. THE GUIDANCE SHOW SEVERAL LOBES OF VORTICITY ROTATING ACROSS THE SOUTHERN PLAINS/LOWER MS VALLEY BUT UNCERTAINTY IS HIGH WITH EXACTLY WHERE THESE IMPULSES WILL DEVELOP. A GENERAL MODEL COMPROMISE SHOULD COVER THIS WITH CONFIDENCE BEING AVERAGE GIVEN THE LOW PROBABILITY OF THE FORECAST LATER IN THE PERIOD. ...SERIES OF SHORTWAVES MARCHING FROM THE WEST COAST INTO THE NORTH-CENTRAL U.S. THROUGH 03/1200Z... FINAL PREFERENCE: BLEND OF THE 00Z ECMWF/12Z ECMWF ENSEMBLE MEAN THROUGH 72 HOURS FOLLOWED BY THE 12Z ECMWF ENSEMBLE MEAN FOR THE REMAINING 12 HOURS FORECAST CONFIDENCE: AVERAGE...THEN BECOMING BELOW AVERAGE TO BEGIN THE PERIOD...BROAD SOUTHWESTERLY FLOW WILL PREVAIL FROM THE WESTERN U.S. INTO THE CENTRAL/NORTHERN HIGH PLAINS FEATURING A SERIES OF SMALLER-SCALE IMPULSES TO CONTEND WITH. THE INITIAL SHORTWAVE CURRENTLY MIGRATING FROM THE CENTRAL HIGH PLAINS TOWARD THE NORTHERN PLAINS/UPPER MIDWEST HAS BEEN A FOCUS FOR WIDESPREAD CONVECTION. MODELS APPEAR TO HAVE A REASONABLE HANDLE ON IT GIVEN THE SHORT-TERM NATURE OF THE FORECAST. FURTHER UPSTREAM...A MORE AMPLIFIED UPPER TROF ACROSS THE WESTERN U.S. WILL COME OUT IN TWO PARTS. THE MORE SOUTHERN ENERGY ACROSS CENTRAL/NORTHERN CA ON SATURDAY EVENING IS A BIT FURTHER WEST IN THE 12Z ECMWF ENSEMBLE MEAN WITH OTHER MODELS OFF TOWARD THE EAST. THIS SUGGESTS A SLIGHT EAST JOG IN THE 00Z CMC/ECMWF SOLUTIONS. THIS SYSTEM GRADUALLY SHEARS AS THE FLOW FLATTENS OUT WITH MORE FOCUS ON THE NORTHERN MOST IMPULSE CROSSING THE NORTHERN HIGH PLAINS BY 02/0000Z. THE 21Z SREF MEAN IS DECIDEDLY SLOWER ON SUNDAY EVENING RELATIVE TO THE STRONGER CONSENSUS DOWNSTREAM. EVENTUALLY THE 00Z NAM CLOSES OFF AN UPPER LOW ALONG THE ND/MN BORDER BY 03/0000Z WHICH SLOWS THE EASTWARD PROGRESSION OF THE SYSTEM. THE SURFACE ALSO LOOKS FAIRLY UNCERTAIN WITH THE PLACEMENT OF THE WAVY FRONTAL BOUNDARY AND ASSOCIATED CONVECTIVE OUTFLOW BOUNDARIES. OVERALL THE 564-DM SPAGHETTI PLOTS SHOW REASONABLE SUPPORT FOR THE 00Z ECMWF/12Z ECMWF ENSEMBLE MEAN WITH THE SYSTEM OVER THE NORTHERN PLAINS/UPPER MIDWEST WITH MORE SPREAD EVIDENT BY LATE MONDAY/EARLY TUESDAY ACROSS THE SOUTHWESTERN U.S. HOWEVER...THE DIFFERENCE BETWEEN THE GEFS/ECMWF ENSEMBLE MEMBERS ARE MUCH LOWER THAN PREVIOUS MODEL CYCLES. IT APPEARS THE FASTER GEFS MEMBERS HAVE SLOWED MORE TOWARD THE ECMWF ENSEMBLE DURING THE PAST TWO CYCLES. MODEL TO MODEL CONTINUITY IS FAIRLY INCONSISTENT WITH THIS FEATURE AS THE 00Z ECMWF HAS NOW SHIFTED TO A FLATTER/MORE PROGRESSIVE FORECAST TRACK VS ITS PRECEDING RUN. WILL STICK WITH THE 12Z ECMWF ENSEMBLE MEAN FOR THE LATTER PORTION OF THE PERIOD. OVERALL...WILL FAVOR A 12Z ECMWF/ECMWF ENSEMBLE MEAN BLEND THROUGHOUT THE PERIOD GIVEN ALL OF THE ABOVE DISCUSSED. ...UPPER TROF EXITING NEW ENGLAND MIDDAY SATURDAY... FINAL PREFERENCE: GENERAL MODEL CONSENSUS FORECAST CONFIDENCE: HIGH AMPLIFICATION IN THE NORTHERN STREAM WILL PLACE A STRONG UPPER TROF EXITING NEW ENGLAND EARLY IN THE PERIOD. THIS SYSTEM SHOULD QUICKLY PUSH OFFSHORE BY SATURDAY AFTERNOON AS HIGHER MID-LEVEL HEIGHTS BUILD UPSTREAM. ANY DISCERNIBLE DIFFERENCES OCCUR ONCE THE CLOSED LOW IS WELL OFFSHORE AND THUS NOT OF CONSEQUENCE TO THE CONUS. A GENERAL MODEL CONSENSUS SOLUTION IS RECOMMENDED GIVEN THE STRONG MODEL AGREEMENT. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... RUBIN-OSTER