MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 242 PM EDT FRI JUN 26 2015 VALID JUN 26/1200 UTC THRU JUN 30/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. CLOSED CYCLONE FORMING NEAR THE GREAT LAKES SATURDAY & ITS ASSOCIATED SURFACE LOWS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ FINAL PREFERENCE: NON-GFS BLEND CONFIDENCE: ABOVE AVERAGE THE 12Z GFS HAS COME IN FAST/STRONG...VERY SIMILAR TO YESTERDAY'S 12Z RUN PARTICULARLY IN THE DAY 1 TO DAY 2 TIME FRAME. CONSIDERING HOW SLOW THE 00Z RUN WAS...RUN TO RUN INCONSISTENCIES DO NOT ALLOW FOR MUCH CONFIDENCE IN THE 12Z GFS SOLUTION AT THIS TIME THOUGH THE 06Z GFS MAY BE A GOOD COMPROMISE IN LINE WITH THE PREFERENCE. THE 12Z GFS EVENTUALLY FALLS INTO BETTER AGREEMENT WITH OTHER ENSEMBLE SUPPORTED OPERATIONAL GUIDANCE SUCH AS THE ECMWF/CMC BY SUNDAY NIGHT 29/00Z AND POTENTIALLY COULD BE USED THEREAFTER. THE 12Z NAM IS A BIT SLOWER AND WEAKER THAN THE REST OF THE 12Z MODEL GUIDANCE INCLUDING THE ENSEMBLE MEANS BUT STILL IN FAIRLY GOOD AGREEMENT TO RETAIN IT WITHIN THE BLEND. THE 12Z ECMWF STARTS OFF A BIT FURTHER NORTH WITH THE TRACK BUT OTHERWISE IS IN GOOD AGREEMENT WITH THE PREFERRED PRIOR 00Z RUN AND 12Z NAM. THE 12Z CMC CONTINUES TO BE ALIGNED AND NOW THE 12Z UKMET HAS JOINED THE VERY TIGHT CLUSTER. AS SUCH A NON-GFS BLEND IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE. SHORTWAVE/SURFACE LOW DROPPING TOWARDS THE GREAT LAKES MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ FINAL PREFERENCE: BLEND OF 12Z GFS/ECMWF CONFIDENCE: ABOVE AVERAGE EVOLUTION OF SHORTWAVE TROF DIGGING INTO THE VOID ACROSS THE UPPER MISSISSIPPI RIVER VALLEY/WESTERN GREAT LAKES IS IN GOOD AGREEMENT THROUGH SUNDAY BEFORE THE 12Z GFS AND 12Z CMC BEGIN TO LEAN FORWARD (FASTER/STRONGER) DEVELOPING A CLOSED SURFACE LOW OVER THE WESTERN GREAT LAKES COMPARED TO THE 00Z ECMWF AND GEFS/ECMWF ENSEMBLE MEANS. EVENTUALLY THE 12Z NAM BEGINS TO CATCH UP WITH THE DEEPEST SOLUTION AND DEVELOPS THE STRONGEST/MOST CONSOLIDATED LOW OF THE 12Z GUIDANCE. THE 12Z ECMWF HAS COME BACK TO A DEEPER SOLUTION COMPARED TO ITS 00Z RUN BRINGING IT CLOSER TO THE 12Z GFS AND 12Z UKMET. THE 12Z CMC REMAINS A BIT FURTHER WEST AND EVEN THOUGH THESE ARE SMALL DETAILS...THE CMC IS NOT ADDED TO THE BLEND. GIVEN CLOSER PROXIMITY...A CONTINUED BLEND OF THE GFS AND ECMWF IS PREFERRED BUT WITH STRONGER AGREEMENT...SO GOES THE CONFIDENCE IN SUCH SOLUTION. PRONOUNCED RIDGE BUILDING ACROSS THE GREAT BASIN SATURDAY WEAK UPPER TROUGH SCRAPING THE WEST COAST SAT/SUN/MON ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ FINAL PREFERENCE: BLEND OF 12Z GFS/ECMWF CONFIDENCE: ABOVE AVERAGE THE WELL FORECAST ANOMALOUS RIDGE REMAINS CONSISTENT...WITH ONLY THE 00Z UKMET A BIT TOO STRONG COMPARED TO THE REST OF THE GUIDANCE BUT IN BETTER AGREEMENT WITH THE STRENGTH THAN ITS PRIOR RUNS. THE MAJOR DIFFERENCES IN THE MODELS ARE LEFT TO HOW THE CUT-OFF LOW WEST OF CALIFORNIA BEGINS TO MERGE/PHASE WITH THE PACIFIC TROF ENERGY STARTING AROUND 18Z SUNDAY. THE SPEED OF THE SHEARING INTO THE NORTHERN STREAM/PACIFIC TROF IS DIRECTLY RELATED TO THE THE STRENGTH/CONSOLIDATION OF THE UPPER-LOW. THE 12Z ECMWF AND 12Z UKMET ARE INITIALIZED A BIT STRONGER WITH THE ECMWF CLOSELY MATCHING THE GFS WHILE THE 12Z UKMET IS IN LINE WITH THE NAM EVENTUALLY OUTPACING IT BY DAY 3. THE 12Z CMC REMAINS STRONGEST AND SLOWEST. WITH THESE INCLUSIONS...THE 12Z NAM SEEMS OUT OF PHASE A BIT MORE AND SO THE PREFERRED BLEND IS NOW JUST THE 12Z GFS/ECMWF BODING ADDITIONAL CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA