MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 309 AM EDT FRI JUN 05 2015 VALID JUN 05/0000 UTC THRU JUN 08/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION INCLUDING PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. LINGERING UPPER TROUGH OFF THE MID ATLANTIC-SOUTHEAST COAST ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF THE 00Z OPERATIONAL MODELS CONFIDENCE: ABOVE AVERAGE CUT-OFF LOW REMAINS WELL DEFINED OVER EASTERN NORTH CAROLINA BUT WILL BEGIN TO OPEN AND PHASE UNDER INFLUENCE OF SHORTWAVE ACROSS QUEBEC PROGRESSING EAST AS WELL AS DEEPENING NORTHERN STREAM ENERGY OUT OF ONTARIO/HUDSON BAY. WITH THE INCLUSION OF THE 00Z ECMWF/UKMET AND CMC...VERY STRONG AGREEMENT NOW EXISTS WITH THE EVOLUTION OF THE BROAD COASTAL SURFACE TROF WITH AN EMBEDDED SURFACE LOW. THE 00Z CMC HAS HAD THE MOST DRAMATIC CHANGE WITH NO STRONG SURFACE LOW OFF THE FLORIDA COAST AT DAY THREE AND IS MUCH BETTER ALIGNMENT WITH THE FASTER 00Z NAM AND 00Z UKMET WITH PROGRESSION NORTHEAST OF THE SURFACE LOW. THE 00Z GFS REMAINS MOST BROAD WITH THE SURFACE TROF. THE 00Z ECMWF IS THE MOST CENTERED IN TIMING AND STRENGTH AND IS LIKELY THE BEST COMPROMISE WITHIN THE 00Z OPERATIONAL SUITE. NORTHERN STREAM MID-CONTINENTAL TROUGH INTO WESTERN GREAT LAKES BY SUNDAY NIGHT ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z ECMWF/UKMET/NAM/CMC CONFIDENCE: SLIGHTLY ABOVE AVERAGE WITH A FILLING TROF TO THE EAST AND A WEAKENING/RETROGRADING TROF TO THE WEST...THE EVOLUTION OF A MID-CONTINENTAL TROF DEVELOPS FROM THE CANADIAN PRAIRIES INTO THE GREAT LAKES WITH AN ATTENDANT SURFACE LOW TRACKING ACROSS THE NORTHERN U.S. INTO EASTERN ONTARIO BY DAY 3. GIVEN THE OVERALL PATTERN CHANGE...CONFIDENCE IS REDUCED BUT ONLY SLIGHTLY GIVEN GOOD 12Z GEFS AND 12Z ECMWF ENSEMBLE MEMBER AGREEMENT ALONG WITH STRONG CLUSTERING OF THE 00Z OPERATIONAL MODELS PARTICULARLY AT THE SURFACE. ALL 00Z OPERATIONAL MODELS DEVELOP A DUAL SURFACE LOW PATTERN WITH SUBTLE DIFFERENCES ON FAVORING THE NORTHERN (SOUTHEAST MONTANA) OR SOUTHERN LOW (EASTERN COLORADO) ALL CONSOLIDATING ACROSS MINNESOTA-SOUTHERN ONTARIO BY DAY 3. MASS FIELDS IN THE UPPER LEVELS EVOLVE SLIGHTLY DIFFERENTLY WITH THE 00Z GFS APPEARS A BIT FLATTER AND FASTER THAN THE REST OF THE GUIDANCE. HOWEVER...GIVEN THE TIME OF YEAR WITH STRONGER SOUTHERN HIGH PLAINS CONVECTION AND SOUTHWESTERLY FLOW INJECTION OF STEEPER LAPSE RATES...THE 00Z GFS SOLUTION DOES NOT SEEM TO BE UNREALISTIC BUT DIFFERS ENOUGH ALOFT TO NOT INCLUDED IN THE BLENDED PREFERENCE. CONFIDENCE HAS RAISED GIVEN THE ADDITION OF THE 00Z ECMWF/UKMET AND CMC MATCHING THE 00Z NAM AND EARLIER PREFERRED 12Z GEFS MEAN AND 12Z ECMWF ENSEMBLE MEAN. UPPER TROUGH OVER THE SOUTHWEST INFLUENCE OF TROPICAL CYCLONE BLANCA BY SUNDAY NIGHT/MONDAY. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON-CMC BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE THE GUIDANCE SHOWS REASONABLE AGREEMENT WITH THE PROGRESSION AND DEPTH OF THE WESTERN UPPER TROUGH AS IT EJECTS WEAK MESOSCALE IMPULSES INTO THE CENTRAL ROCKIES OVER THE NEXT FEW DAYS. EVENTUALLY THE BASE OF THE TROF RETROGRADES INTO THE PACIFIC OFF OF SOUTHWEST CALIFORNIA AND BAJA CALIFORNIA...STILL IN VERY GOOD AGREEMENT. THE APPROACH OF TROPICAL CYCLONE BLANCA APPEARS TO BE HIGHLY INFLUENTIAL ON THE EVOLUTION OF THE WESTERN TROF AND ITS ORIENTATION BY SUNDAY NIGHT INTO MONDAY. THE 00Z GFS IS THE FASTEST OF THE OPERATIONAL MODELS WITH BLANCA SITUATED OVER THE CENTRAL SEA OF CORTEZ BY THE END OF THE PERIOD. THE NAM IS THE WEAKEST BUT CLUSTERED WELL WITH THE 00Z UKMET AND 00Z ECMWF OVER FAR SOUTHERN BAJA WHILE THE 00Z CMC IS THE SLOWEST. THE RUN TO RUN TRENDS OF THE ENSEMBLE MEANS FOLLOW THEIR OPERATION RUNS...WHICH ARE FASTER...FAVORING THE 00Z GFS RATHER THAN THE 00Z CMC. SINCE THERE IS HIGH AGREEMENT WITH THE 00Z OPERATIONAL RUNS UNTIL THE INFLUENCE OF BLANCA IS FELT... AND FASTER PROGRESSION OF BLANCA IS TRENDING... A NON-CMC BLEND IS PREFERRED AT SLIGHTLY ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA