MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 127 PM EST SAT DEC 24 2016 VALID DEC 24/1200 UTC THRU DEC 28/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION WITH PREFERENCES & CONFIDENCE INTERVALS ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ NAM/GFS INITIALIZATION ISSUES DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. MID-LEVEL LOW DROPPING PARALLEL TO THE WEST COAST ON SUN ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: ECMWF/UKMET COMPROMISE CONFIDENCE: SLIGHTLY BELOW AVERAGE THE 12Z GFS AND ITS ENSEMBLE RETROGRADE THIS SYSTEM MORE TO THE WEST THAN SEEN IN THE OTHER GUIDANCE -- WHICH CAN BE A BIAS. A COMPROMISE OF THE 12Z ECMWF/12Z UKMET LIES BETWEEN THE 00Z ECMWF/12Z GEFS MEANS AND IS PREFERRED WITH SLIGHTLY BELOW AVERAGE CONFIDENCE. CYCLONE MOVING INTO SD LATE SUNDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL COMPROMISE WITH CYCLONE NON-NAM SOLUTION WITH TRAILING COLD FRONT CONFIDENCE: SLIGHTLY ABOVE AVERAGE THERE ARE SOME SLIGHT LATITUDE/PROGRESSION DIFFERENCES AMONGST THE GUIDANCE WITH THE MAIN CYCLONE. WITH THE GEFS MEAN AND ECMWF ECMWF MEAN PEGGED TO THEIR OPERATIONAL RUNS, IT MAKES IT HARD TO RULE AGAINST EITHER. A COMPROMISE OF THE AVAILABLE GUIDANCE IS PREFERRED FOR CYCLONE POSITION AND DEPTH WITH SLIGHTLY ABOVE AVERAGE CONFIDENCE. WITH ITS TRAILING COLD FRONT, THE 12Z NAM APPEARS SLOW WITH ITS PROGRESSION FROM THE MIDWEST TO THE EAST, SO PREFER A COMPROMISE OF THE 12Z CANADIAN/12Z ECMWF/ 12Z UKMET/12Z GFS HERE WITH ABOVE AVERAGE CONFIDENCE. SYSTEM MOVING TOWARDS SOUTHWEST CANADA/PACIFIC NW LATE MON SHORTWAVES EMERGING INTO THE MIDWEST MONDAY NIGHT SHORTWAVE REACHING THE NORTHEAST LATER TODAY SHORTWAVES MOVING BY NEW ENGLAND THROUGH SUNDAY MORNING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ THE GUIDANCE SHOWS GOOD AGREEMENT WITH THESE SYSTEMS, SO PREFER A COMPROMISE OF THE AVAILABLE GUIDANCE TO DEAL WITH LINGERING DETAIL ISSUES WITH ABOVE AVERAGE CONFIDENCE. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... ROTH