MODEL DIAGNOSTIC DISCUSSION NWS WEATHER PREDICTION CENTER COLLEGE PARK MD 1203 PM EST MON DEC 14 2015 VALID DEC 14/1200 UTC THRU DEC 18/0000 UTC ...SEE NOUS42 KWNO (ADMNFD) FOR THE STATUS OF THE UPPER AIR INGEST... 12Z NAM/GFS EVALUATION...INCLUDING PRELIMINARY PREFERENCES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ CLOSED LOW MOVING THROUGH THE GREAT LAKES TONIGHT WITH ACCOMPANYING SURFACE LOW SURFACE LOW DEVELOPING OFF THE NEW ENGLAND COAST EARLY TUE ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: GENERAL MODEL COMPROMISE CONFIDENCE: ABOVE AVERAGE NO SIGNIFICANT MODEL DIFFERENCES WERE NOTED WITH THIS SYSTEM. CLOSED LOW MOVING THROUGH THE PLAINS TUE/WED SURFACE LOW/ACCOMPANYING FRONT MOVING ACROSS THE MISSISSIPPI VALLEY ON WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z NAM/00Z ECMWF BLEND CONFIDENCE: AVERAGE THERE IS RELATIVELY SMALL SPREAD IN THE ENSEMBLE GUIDANCE AT 00Z/16 AND 12Z/16 REGARDING THE LOW-MID LEVEL LOW TRACKING ACROSS THE UPPER MIDWEST. WHILE THE 12Z GFS IS LOCATED WITHIN THE CLUSTERING OF ENSEMBLE MEMBERS...IT IS TOWARD THE FASTER SIDE WITH THE TRACK OF THE LOW. BETTER CLUSTERING IS IN FAVOR OF A POSITION NEAR THE 12Z NAM AND 00Z ECMWF. MID-LEVEL SHORTWAVE DIGGING SOUTH ACROSS THE NRN ROCKIES ON WED ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/00Z ECMWF BLEND CONFIDENCE: AVERAGE THE DEEPER 00Z UKMET/CMC ALIGN WITH THE MINORITY OF ENSEMBLE MEMBERS INDICATING A DEEPER SHORTWAVE TROUGH ACROSS THE NRN ROCKIES BY WED EVENING. THE 00Z/14 GEFS/EC/CMC ENSEMBLES...EC MEAN/GEFS MEAN SUPPORT A FLATTER TROUGH COMING ACROSS THE REGION. ENSEMBLE SPREAD INCREASES TOWARD THU ACROSS THE FOUR CORNERS REGION BUT THE 00Z UKMET/CMC ARE CERTAINLY SLOW OUTLIERS WITH THE REMAINING MODELS FASTER. THE 00Z ECMWF IS DEEPER THAN ITS ENSEMBLE MEAN BUT AGREES WELL WITH THE TIMING OF THE 12Z NAM/GFS. THE NAM DOES NOT FIT IN WITH THE OTHER MODELS EARLIER IN THE FORECAST...SO AT THE MOMENT...A BLEND OF THE DEEPER 00Z ECMWF AND LESS DEEP 12Z GFS WILL IS PREFERRED. LARGE CLOSED LOW/PACIFIC FRONT NEARING THE PACIFIC NORTHWEST THU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ PREFERENCE: 12Z GFS/00Z ECMWF BLEND CONFIDENCE: BELOW AVERAGE THE NAM/GFS ARE QUICKER TO BRING A WARM FRONT TO THE PACIFIC NORTHWEST...WITH THE NAM FASTEST. THE ENSEMBLES MADE A SIGNIFICANT SHIFT TO BE FASTER WITH THE TIMING OF THE ASSOCIATED UPPER TROUGH APPROACHING THE WEST COAST OF NORTH AMERICA WITH THE 00Z/14 CYCLE. CONFIDENCE IS LIMITED GIVEN THE SOURCE REGION OF THE SHORTWAVE...BUT A BLEND OF THE GFS/ECWMF IS PREFERRED GIVEN THE UNCERTAINTY AND THE FACT THAT THEY LIE IN THE MIDDLE OF THE LATEST DETERMINISTIC/ENSEMBLE SPREAD. www.wpc.ncep.noaa.gov/html/model2.shtml... www.wpc.ncep.noaa.gov/h5pref/h5pref.shtml... OTTO