MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 148 PM EST WED JAN 11 2017 VALID JAN 11/1200 UTC THRU JAN 15/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z MODEL EVALUATION INCLUDING FINAL PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ CYCLONIC FLOW/SHORTWAVES SINKING ACROSS NORTHERN PLAINS ASSOCIATED FLAT SURFACE WAVE ACROSS GREAT LAKES EARLY THURS SURFACE WAVE CURVING THROUGH THE CANADIAN PRAIRIES EARLY THURSDAY ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE TODAYS 12Z GFS IS A BIT FASTER WITH THE SURFACE LOW ACROSS NEW ENGLAND ON THU...AND WHILE THIS WAS ALSO THE CASE YESTERDAY...TRENDS SINCE YESTERDAY HAVE EDGED FASTER TOWARD THE PREVIOUS GFS. ENSEMBLE TRENDS AND THE LATEST 12Z NAM/GFS ALSO HOLD ONTO A SECOND LOW WITH A DOUBLE BARREL FEATURE APPEARING BY 00Z/13 ACROSS FAR NRN NEW ENGLAND INTO THE CANADIAN MARITIMES. MINOR ADJUSTMENTS WERE SEEN IN THE 12Z ECMWF/UKMET/CMC RELATIVE TO THEIR PREVIOUS RUNS. GIVEN THE SMALL SCALE DIFFERENCES...RECOMMEND TO GO WITH A GENERAL MODEL BLEND...WHICH WOULD SLOW DOWN THE 12Z GFS POSITION SOME BUT NOT TO THE SLOWER EDGE OF THE SPECTRUM. WEAK SHORTWAVE CROSSING THE PLAINS TONIGHT...EVENTUALLY REACHING THE OHIO VALLEY AND GREAT LAKES BY THU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: AVERAGE ONLY MINOR DIFFERENCES WITH THIS FEATURE WERE NOTED...WITH A GENERAL MODEL COMPROMISE RECOMMENDED TO SMOOTH OUT THESE SMALLER SCALE DIFFERENCES. CLOSED LOW OVER THE SRN WEST COAST FOR THE END OF THE WEEK ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: NON 12Z NAM BLEND CONFIDENCE: SLIGHTLY ABOVE AVERAGE EARLY IN THE FORECAST...BY 12Z/12...THE 00Z ECMWF WAS NOTED TO BE SLIGHTLY WEAKER THAN THE DETERMINISTIC/ENSEMBLE CONSENSUS REGARDING LOW PRESSURE NEAR THE CNTRL CA COAST BUT THE 12Z ECMWF HAS INCREASED IN STRENGTH. THERE IS NOW DECENT AGREEMENT WITH THIS LOW ALONG THE CA COAST WITH ONLY MINOR PLACEMENT AND STRENGTH DIFFERENCES. BEYOND THU NIGHT...OR 00Z/13...THE CLOSED LOW THAT FORMS AND BEGINS TO MOVE EASTWARD ACROSS THE SWRN U.S. SHOWS SOME SMALLER SCALE DIFFERENCES. THE 00Z ECMWF LOOKED WEAKER WITH LOW-MID LEVEL RIDGING CENTERED ACROSS THE SOUTHEAST COMPARED TO ITS MEAN...WHICH MAY ALLOW THE 00Z ECMWF TO ADVANCE THE CLOSED LOW QUICKER TOWARD THE EAST. THE 12Z ECMWF INCREASED THE STRENGTH OF THE RIDGE DOWNSTREAM AND SLOWED THE PROGRESSION OF THE UPPER LOW...FALLING CONSISTENT WITH TRENDS IN THE ENSEMBLE GUIDANCE TO BE SLOWER AND SLIGHTLY WEAKER WITH THE CLOSED LOW THROUGH FRI NIGHT. COMPARING ALL OF THE 12Z DETERMINISTIC GUIDANCE THERE WAS RELATIVELY GOOD CONSENSUS AMONG THE MODELS...BUT A NON 12Z NAM BLEND SEEMED BEST HERE GIVEN THE NAM WAS FARTHEST NORTH AND SLIGHTLY QUICKER WITH THE PROGRESSION OF THE UPPER LOW EASTWARD THROUGH FRI. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO