MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1147 PM EST SUN FEB 14 2016 VALID FEB 15/0000 UTC THRU FEB 18/1200 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 00Z NAM/GFS EVALUATION WITH PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ GFS/NAM INITIALIZATION ERRORS DO NOT SEEM TO DEGRADE THEIR SHORT RANGE FORECASTS. LARGE UPPER TROUGH IMPACTING THE WEST COAST WED/THU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE THERE IS SURPRISINGLY GOOD MODEL AGREEMENT WITH THIS TROUGH ACROSS THE WEST COAST GIVEN THE DAY 3 TIME FRAME. A GENERAL MODEL COMPROMISE IS PREFERRED TO AVERAGE OUT SMALLER SCALE DIFFERENCES. LOW PRESSURE TRACKING FROM THE LOWER MISSISSIPPI VALLEY TO THE NORTHEAST THROUGH TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 12Z ECMWF BLEND CONFIDENCE: AVERAGE ENSEMBLE SCATTER LOW PLOT TRENDS HAVE SHOWN A SHIFT TO THE WESTERN SIDE OF THE SOLUTION ENVELOPE BY TUE MORNING ACROSS THE APPALACHIANS...AND THE 00Z NAM/GFS ARE BOTH ON THE ERN EDGE OF THE ENSEMBLE LOW PLOTS BY 12Z/16. THE 12Z ECWMF SEEMS TO MATCH CLOSER TO THE MIDDLE OF THE LATEST CLUSTERING BUT GIVEN THE FACT THAT THE GFS/NAM HAVE BEEN CONSISTENT WITH THEIR PAST 2 OR 3 CYCLES TOWARD THE EAST...FEEL THE ECMWF MAY TREND TOWARD THE 00Z GFS WITH ITS 00Z CYCLE. BEYOND 12Z/16...A BLEND OF THE 12Z ECMWF AND 00Z GFS MATCHES CLOSEST TO THE BEST ENSEMBLE CLUSTERING WHILE THE 00Z NAM SEEMS TO TRACK THE LOW TOO FAR TO THE EAST. THE 12Z UKMET DOES NOT SHOW PHASING OF SHORTWAVES OVER THE MISSISSIPPI VALLEY AND THEREFORE DOES NOT ATTAIN THE STRENGTH OF THE REMAINING MODEL CONSENSUS WITH THE SURFACE LOW AS IT TRACKS UP THE EAST COAST...AND SO THE 12Z UKMET IS CONSIDERED VERY UNLIKELY. MID-LEVEL SHORTWAVE CROSSING THE MID-MISSISSIPPI VALLEY TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 00Z GFS / 12Z ECMWF CONFIDENCE: SLIGHTLY BELOW AVERAGE ENSEMBLE SCATTER LOW PLOT TRENDS CURRENTLY SHOW A FAIR DEGREE OF NORTH/SOUTH SPREAD WITH A SURFACE LOW IN IOWA/MISSOURI TUE MORNING. THE 00Z NAM IS TOWARD THE NORTH SIDE OF THE SPREAD WHILE THE 12Z UKMET/CMC ARE ON THE FAR SOUTH SIDE. WHILE THE 00Z GFS IS ON THE EAST SIDE OF THE LOW PLOTS...THE 00Z GFS AND THE 12Z ECMWF ARE THE BEST MATCH THROUGH TUE MORNING WITH THE ENSEMBLES. BEYOND TUE MORNING...THE 00Z NAM/GFS REMAIN ON THE NORTH SIDE OF A MID-LEVEL VORTICITY MAX CROSSING THE LOWER OHIO VALLEY WHILE THE 12Z ECMWF/UKMET/CMC ARE SOUTH OR SLOWER. SPLITTING THE DIFFERENCES BETWEEN THE GFS/ECMWF PROVIDES A COMPROMISE THAT IS WITH THE CENTER OF THE LATEST ENSEMBLE CLUSTERING. FRONT REACHING THE PACIFIC NORTHWEST LATE THIS EVENING ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE MODELS SHOW SIMILARLY WITH THIS SYSTEM. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO