MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 232 PM EDT THU JUN 18 2015 VALID JUN 18/1200 UTC THRU JUN 22/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. SYSTEM APPROACHING THE PACIFIC NORTHWEST LATE SUNDAY COLD FRONT MOVING THROUGH THE NORTHEAST THU/FRI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THE GUIDANCE SHOWS REASONABLE AGREEMENT WITH THESE SYSTEMS. LOW NEAR THE GREAT LAKES SAT NIGHT/SUN MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: CANADIAN/ECMWF COMPROMISE CONFIDENCE: BELOW AVERAGE A COMPROMISE OF THE 12Z CANADIAN/12Z ECMWF SOLUTIONS IS CLOSE TO THE 00Z GLOBAL ENSEMBLE CLUSTERING SURFACE LOW-WISE, WHICH HAS CHANGED A BIT FROM DAY TO DAY AND ALSO KEEPS THE LOW ON AN EAST-WEST TRACK, WHICH BEFITS THE ZONAL FLOW ITS FLAT PARENT SHORTWAVE IS EMBEDDED WITHIN. THIS PREFERENCE IS PREFERRED WITH BELOW AVERAGE CONFIDENCE DUE TO THE DAY-TO-DAY AND RUN-TO-RUN CHANGES IN THE GUIDANCE. TROPICAL DEPRESSION BILL ~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: CLOSEST TO A NAM/ECMWF COMPROMISE CONFIDENCE: AVERAGE/SEE LATEST WPC ADVISORY THE 12Z NAM/12Z ECMWF SEEM TO HAVE THE BEST HANDLE ON THIS SYSTEM. THE 12Z GFS/00Z CANADIAN LOSE THE SURFACE LOW FOR THE SYSTEM AS IT TRACKS THROUGH THE OHIO VALLEY. SINCE THE SYSTEM HAS BARELY WEAKENED SINCE LANDFALL, THINK A MORE DEFINED LOW IS A GOOD IDEA. HOWEVER, THE 12Z UKMET IS UP TO ITS OLD TRICKS WITH BILL AND DEEPENS THE SYSTEM AFTER CROSSING THE APPALACHIANS. PER COORDINATION WITH OPC, THE UKMET IS A LOW PROBABILITY ALTERNATIVE SCENARIO. FOR THE LATEST... PLEASE REFER TO THE LATEST WPC ADVISORY FOR BILL... INCLUDING STORM TOTAL RAINFALL AMOUNTS. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH