MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 103 AM EDT TUE JUN 02 2015 VALID JUN 02/0000 UTC THRU JUN 05/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z MODEL EVALUATION...INCLUDING PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ WELL DEVELOPED NORTHERN STREAM UPPER LOW ROLLING ACROSS NEW ENGLAND WEAK SURFACE LOW AFFECTING MID-ATLANTIC THRU COASTAL NEW ENGLAND ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF OPERATIONAL MODELS CONFIDENCE: ABOVE AVERAGE A WELL DEVELOPED AND CONSOLIDATED UPPER LOW ALONG THE ONTARIO/QUEBEC BORDER SHIFTS SHIFTS EASTWARD CLIPPING NORTHERN NEW ENGLAND TUESDAY INTO WEDNESDAY EVENTUALLY PULLING A WEAK SURFACE REFLECTION OUT THE MID-ATLANTIC AND DEEPENING IT OFF NOVA SCOTIA. THE MODELS CONTINUE TO SHOW VERY GOOD AGREEMENT WITH PLACE AND INTENSITY FOR THE LARGER SCALE FEATURE UNTIL THE SYSTEM IS OUT OF CONUS ON WEDNESDAY NIGHT. A BLEND OF THE OPERATIONAL MODEL RUNS IS PREFERRED WITH ABOVE AVERAGE CONFIDENCE. SLOW MOVING CLOSED LOW OVER TENNESSEE RIVER VALLEY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z NAM/GFS AND 12Z ECMWF ENSEMBLE MEAN CONFIDENCE: ABOVE AVERAGE THROUGH 00Z WED... SLIGHTLY BELOW AVERAGE AFTER A WELL DEFINED UPPER LOW CURRENTLY CENTERED ON THE CENTRAL KENTUCKY/TENNESSEE BORDER SLOWLY SHIFTS EASTWARD ACROSS THE SOUTHERN APPALACHIANS INTO THE CAROLINAS. THERE IS FAIRLY GOOD AGREEMENT WITH THE TRACK AND DEPTH OF THE CLOSED LOW UNTIL ABOUT 12Z WEDNESDAY. THE 00Z NAM/GFS MAY BE STARTING A TREND OF BROADENING THE TROF TO THE EAST AS IT SHOWS PULSES OF SHORTWAVE ENERGY EJECTING OUT OF BROAD SOUTHWESTERLY FLOW FROM THE WESTERN CARIBBEAN. CURRENT CONVECTIVE TRENDS IN THE VICINITY GIVE SOME CREDENCE TO THIS SOLUTION OF CARIBBEAN INFLUENCE. ADDITIONAL CONFIDENCE IS ADDED WITH A HANDFUL OF 12Z ECMWF ENSEMBLE MEMBERS HINTING THIS DIRECTION AS WELL. THE 12Z UKMET SEEMS TO OPEN THE TROF AND WEAKEN IT A BIT TOO QUICK WHILE THE 12Z CMC IS SLOWER KEEPING MORE ENERGY IN THE BASE OF THE UPPER TROF AS A CLOSED LOW...ELIMINATING THEM FROM THE PREFERRED BLEND OF THE 00Z NAM/GFS WITH INCLUSION OF THE 12Z ECMWF ENSEMBLE MEAN TO HELP TEMPER THE LARGER SHIFT. SHORTWAVE SHEARING OUT ALONG U.S./CANADIAN BOARDER NORTHERN HIGH PLAINS CYCLOGENESIS SOUTHERN STREAM SHORTWAVE EJECTING INTO CENTRAL PLAINS THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: BLEND OF 00Z NAM/GFS CONFIDENCE: AVERAGE ENERGY AT THE BASE OF NEGATIVE TILT PACIFIC TROF AT THE BEGINNING OF THE PERIOD IS EJECTING ACROSS THE NORTHERN U.S. ROCKIES EVENTUALLY SHEARING OUT ALONG THE U.S. CANADIAN BOARDER BY DAY 2. A SURFACE LOW OVER EASTERN MONTANA MOVES EASTWARD AND BEGINS TO WEAKEN INTO AN SOUTHWEST TO NORTHEAST ORIENTED SURFACE TROF NEAR WESTERN LAKE SUPERIOR BY WEDNESDAY AFTERNOON. THIS SURFACE TROF CONNECTS TO A PERSISTENT CYCLONE ALONG THE COLORADO HIGH PLAINS UNTIL SHIFTING EAST AND WEAKENING AS SUBTLE SHORTWAVE EJECTS AND SPINS UP OVER NEBRASKA ON THURSDAY. THE 12Z CMC APPEARS TO BE THE MOST OUT OF PHASE WITH THE OTHER OPERATIONAL GUIDANCE AS IT OVER AMPLIFIES AN UPPER LEVEL TROF ACROSS MINNESOTA BY DAY 3 WITH A MUCH STRONGER SURFACE REFLECTION. THE 12Z ECMWF ALSO SEEMS A BIT TOO STRONG WITH SOME POTENTIAL CONVECTIVE FEEDBACK INTO SHORTWAVE EJECTING ON DAY 3 ACROSS THE CENTRAL PLAINS. GIVEN THE TIMING OF THE EJECTION...FORCING CONVECTION AROUND THE 06Z TIME FRAME LENDS LESS CREDIBILITY FOR ITS SOLUTION THOUGH IT IS WEAK. LEAVING THE 00Z GFS/NAM WHICH IN GOOD AGREEMENT WITH THE GEFS MEANS BUT ALSO WITHIN SOME OF THE 12Z ECMWF ENSEMBLE MEMBERS THROUGH DAY 3. IT REMAIN A BIT SLOWER AND LESS AMPLIFIED THAN THE 12Z ECWMF WITH THE EJECTION OF THE SHORTWAVE INTO CENTRAL PLAINS ON THURSDAY BUT IS SUPPORTED WITH A STRONG CLUSTERING OF GEFS SOLUTIONS PROVIDING BETTER CONFIDENCE ESPECIALLY GIVEN BETTER TIMING OF WITH CONVECTIVE RESPONSE. UPPER TROUGH RELOADING OVER THE WEST BY WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 12Z CMC BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE STRONG PACIFIC WESTERLY JET ENTERS THE PACIFIC COASTAL ZONE BY WEDNESDAY DROPPING A BULK OF ENERGY INTO THE DEEPENING OF UPPER LEVEL LOW ALONG THE CALIFORNIA COAST BY THE END OF THE FORECAST PERIOD. REMARKABLE ECMWF AND NAEFS ENSEMBLE AGREEMENT IN THE EVOLUTION OF THIS SYSTEM. THE GEFS MEMBERS ALONG WITH THE GFS HAVE BEEN THE WESTERN MEMBERS WHILE THE CMC MEMBERS THE FURTHEST EAST. THE 12Z CMC CONTINUES TO BE THE MOST PROGRESSIVE OUTLIER AND SHOULD BE USED WITH CAUTION....BUT THE 00Z NAM/GFS AND 12Z ECMWF ALL APPEAR TO BE GOOD REPRESENTATIVES TO PROVIDE SLIGHTLY ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA