MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 112 PM EDT MON JUN 15 2015 VALID JUN 15/1200 UTC THRU JUN 19/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. TROPICAL DISTURBANCE MOVING TOWARDS TX ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRELIMINARY PREFERENCE: 00Z ECMWF BEFORE 00Z/18 --- BLEND OF 12Z NAM/GFS/ 00Z ECMWF AFTER CONFIDENCE: BELOW AVERAGE/SEE NHC OUTLOOKS THERE APPEAR TO BE TWO SOLUTION CAMPS WITH THE EVOLUTION OF THE CYCLONE AS IT PROGRESSES WEST AND NORTH TOWARD TEXAS. THE 00Z CMC/UKMET BRING MORE CONSOLIDATED ENERGY NORTHWARD INTO CENTRAL TEXAS...WHILE THE 12Z NAM/GFS AND 00Z ECMWF MOVE THE SURFACE CYCLONE FURTHER WEST INTO SOUTH TEXAS WHILE SHEARING ENERGY BACK TOWARD NORTHEAST TEXAS. THE 00Z ECMWF CONTINUED TO BE THE BEST MIDDLE GROUND SOLUTION...UNTIL SOME CONVECTIVE FEEDBACK AT 00Z/18 TENDED TO OVER STRENGTHEN THE LOWER LEVELS OF THE CYCLONE...MAKING IT LESS DESIRABLE AFTER THAT POINT AND SIGNIFICANTLY REDUCING THE CONFIDENCE...IN ANY PARTICULAR SOLUTION. USE OF THE 12Z NAM/GFS AND 00Z ECMWF BLEND MAY BE THE BEST COMPROMISE AFTER 00Z/18. CLOSED LOW NEAR VANCOUVER ISLAND THROUGH MID WEEK ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRELIMINARY PREFERENCE: 00Z GFS/ECMWF/CMC BLEND CONFIDENCE: AVERAGE THE 12Z NAM CONTINUES TO BE THE SLOWEST TO MOVE THE CLOSED LOW NEARING SOUTHWEST BRITISH COLUMBIA...WHILE THE 00Z UKMET IS THE FASTEST....BOTH BEING A BIT UNREALISTIC ON EITHER SIDE OF THE ENSEMBLE SPREAD. THE 00Z ECMWF CONTINUES TO BE THE MIDDLE GROUND WITH THE EVOLUTION OF THE UPPER LOW... THOUGH THERE IS GOOD SUPPORT FROM THE 12Z GFS (THOUGH INITIALLY STARTING OUT SLOW) AND THE 00Z CMC (THOUGH INITIALLY STARTING OUT FAST). GIVEN THE RUN TO RUN CONTINUITY OF THE ECMWF...ENHANCED WEIGHTING TOWARD THE 00Z ECMWF IS PREFERRED WITHIN A BLEND WITH THE 12Z GFS/CMC AT THIS TIME WITH AVERAGE CONFIDENCE LOW AMPLITUDE SHORTWAVE REACHING THE NRN PLAINS TUE EVENING SURFACE WAVE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRELIMINARY PREFERENCE: BLEND OF OPERATIONAL MODELS CONFIDENCE: SLIGHTLY ABOVE AVERAGE WHILE DIFFERENCES AT 500 MB ARE MINIMAL...THE 12Z NAM CONTINUES TO BE STRONGER AND PLACED SOUTHEAST INITIALLY BUT EVENTUALLY COMES INTO AGREEMENT WITH GOOD CLUSTERING OF SURFACE LOW AFTER THE INITIAL DEVELOPMENT AS THE LOW DEVELOPS ALONG LEE OF THE ROCKIES AND INTO SAND HILLS AND MIDWEST BY WED NIGHT. GOOD ENOUGH AGREEMENT EXISTS WITH THE OTHER OPERATIONAL MODELS AS WELL WITH THE ECMWF BEING THE WEAKEST MEMBER BUT NOT ENOUGH TO REMOVE FROM A PREFERRED BLEND OF THE OPERATIONAL MODELS. THIS IS ALSO SUPPORTED BY THE ENSEMBLE MEANS PROVIDING SLIGHTLY ABOVE AVERAGE CONFIDENCE. TROUGH OVER CENTRAL CANADA WED AND COLD FRONTAL POSITION INTO THE NORTHERN PLAINS LATE WED/THURS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRELIMINARY PREFERENCE: BLEND 00Z ECMWF/ECMWF ENSEMBLE MEAN CONFIDENCE: AVERAGE VERY GOOD AGREEMENT EXISTS WITH THE DEEPENING OF THE CENTRAL CANADIAN TROF THROUGH WEDNESDAY. EVENTUALLY THE 12Z NAM/GFS BEGIN TO BECOME A BIT DEEPER COMPARED TO THE ECMWF AND ITS ENSEMBLE MEMBERS. THIS HAS BEEN CONSISTENT WITH THE LAST FEW RUNS BUT LIKEWISE THE ECMWF HAS BEEN QUITE CONSISTENT WITH FLATTER SOLUTION. THERE IS ADDITIONAL SUPPORT FOR THE ECMWF WITH THE 00Z CMC AS ITS ENSEMBLE MEMBERS AS WELL. THERE IS VERY LITTLE IMPACT WITH THE SPEED/LOCATION OF THE SURFACE FRONT EXCEPT WITH A SLIGHTLY STRONGER LOW WITH THE 12Z NAM SHIFTED SOUTH AND WEST ALONG THE FRONT ACROSS NORTHWEST ONTARIO. WITH SOME SPREAD...ONLY AVERAGE CONFIDENCE IN USING A BLEND OF THE 00Z ECMWF AND ITS ENSEMBLE MEAN. SHORTWAVE MOVING EAST FROM CNTRL PLAINS INTO NEW ENGLAND MON-TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PRELIMINARY PREFERENCE: BLEND OF OPERATIONAL MODELS CONFIDENCE: SLIGHTLY ABOVE AVERAGE FAIRLY GOOD AGREEMENT CONTINUES WITH THE EASTWARD PROGRESSION OF THIS SYSTEM...WITH ONLY SUBTLE DIFFERENCES IN HANDLING LOWER LEVEL/SURFACE MASS/WIND WITH TRANSLATION OVER/THRU APPALACHIANS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... GALLINA